Glossary

Jessie A. Key

Term Definition Section of Book
abbreviated electron configuration An electron configuration that uses one of the noble gases to represent the core of electrons up to that element Organization of Electrons in Atoms
absolute zero The minimum possible temperature, labeled 0 K (zero kelvins) Other Units: Temperature and Density
acid An ionic compound of the H+ cation dissolved in water Acids
acid A compound that increases the amount of H+ ions in an aqueous solution Neutralization Reactions
acid dissociation constant (Ka) The equilibrium constant for the dissociation of a weak acid into ions Some Special Types of Equilibria
acid salt An ionic compound whose aqueous solution is slightly acidic Strong and Weak Acids and Bases and Their Salts
activated complex See transition state Reaction Mechanisms
activation energy (Ea) The minimum amount of kinetic energy molecules must possess for an effective collision to occur Factors that Affect the Rate of Reactions
active site Area of enzymatic action where substrate molecules react Catalysis
activity series A list of elements that will replace elements below them in single-replacement reactions Types of Chemical Reactions: Single- and Double-Displacement Reactions
actual yield The amount that is actually produced in a chemical reaction Yields
addition reaction A reaction where atoms are added across a double or triple bond Hydrocarbons
adhesion The tendency of a substance to interact with other substances because of intermolecular forces Properties of Liquids
adsorb Bind to the surface of another substance Catalysis
alcohol An organic compound that contains an OH functional group Alkyl halides and alcohols
aldehyde A compound that has a carbonyl functional group at the end of a chain of C atoms Other Oxygen-Containing Functional Groups
aliphatic hydrocarbons A hydrocarbon based on chains of C atoms Hydrocarbons
alkaline battery A type of dry cell that contains an alkaline (i.e., basic) moist paste, rather than an acidic paste Applications of Redox Reactions: Voltaic Cells
alkane An aliphatic hydrocarbon with only single covalent bonds Hydrocarbons
alkene An aliphatic hydrocarbon that contains a C–C double bond Hydrocarbons
alkyl halide An organic compound that contains a halogen atom Alkyl halides and alcohols
alkyne An aliphatic hydrocarbon that contains a C–C triple bond Hydrocarbons
alpha particle A type of radioactive emission equivalent to a helium nucleus Radioactivity
amide group A functional group that is the combination of the amine and carbonyl functional groups Other Functional Groups
amide bond The bond between the N atom and the C atom in an amide. Other Functional Groups
amine An organic derivative of ammonia Other Functional Groups
amorphous solid A solid with no long-term structure or repetition Solids
amphiprotic A substance that can act as a proton donor or a proton acceptor Brønsted-Lowry Acids and Bases
analyte The reagent of unknown concentration Acid-Base Titrations
angular momentum quantum number (ℓ) An index that affects the energy and the spatial distribution of an electron in an atom Quantum Numbers for Electrons
anion A species with an overall negative charge Ions and Ionic Compounds
anode The half cell that contains the oxidation reaction Applications of Redox Reactions: Voltaic Cells
antibonding molecular orbital A higher energy molecular orbital generated by destructive combination of atomic orbitals Molecular Orbitals
aromatic hydrocarbons Flat ring systems, which contain continuously overlapping p orbitals, such as benzene Hydrocarbons
Arrhenius acid A compound that increases the hydrogen ion concentration in aqueous solution Arrhenius Acids and Bases
Arrhenius base A compound that increases the hydroxide ion concentration in aqueous solution Arrhenius Acids and Bases
atmosphere (atm) A unit of pressure equal to the average atmospheric pressure at sea level; defined as exactly 760 mmHg Pressure
atom The smallest piece of an element that maintains the identity of that element Atomic Theory
atomic mass The sum of the number of protons and neutrons in a nucleus Atomic Theory
atomic mass The weighted average of the masses of the isotopes that compose an element Masses of Atoms and Molecules
atomic mass unit One-twelfth of the mass of a carbon-12 atom Masses of Atoms and Molecules
atomic number The number of protons in an atom Atomic Theory
atomic radius An indication of the size of an atom Periodic Trends
atomic symbol A one- or two-letter representation of the name of an element Atomic Theory
atomic theory The concept that atoms play a fundamental role in chemistry Atomic Theory
aufbau principle (German for “building up”):  electrons fill the lowest energy orbitals first. Organization of Electrons in Atoms
autoionization constant of water (Kw) The product of the hydrogen ion and hydroxide ion concentrations Autoionization of Water
autoionization of water Water molecules act as acids (proton donors) and bases (proton acceptors) with each other to a tiny extent in all aqueous solutions Autoionization of Water
Avogadro’s law A gas law that relates number of particles to volume Other Gas Laws
balanced chemical equation A condition when the reactants and products of a chemical equation have the same number of atoms of all elements present The Chemical Equation
base A compound that increases the amount of OH− ions in an aqueous solution Neutralization Reactions
basic salt An ionic compound whose aqueous solution is slightly basic Strong and Weak Acids and Bases and Their Salts
becquerel (Bq) A unit of radioactivity equal to 1 decay per second Units of Radioactivity
beta particle A type of radioactive emission equivalent to an electron Radioactivity
boiling (or vaporization) The process of a liquid becoming a gas Phase Transitions: Melting, Boiling and Subliming
boiling point The characteristic temperature at which a liquid becomes a gas Phase Transitions: Melting, Boiling and Subliming
boiling point elevation The increase of a solution’s boiling point because of the presence of solute Colligative Properties of Solutions
boiling point elevation constant (Kb) The constant that relates the molality concentration of a solution and its boiling point change Colligative Properties of Solutions
bond energy The approximate amount of energy needed to break a covalent bond Other Aspects of Covalent Bonding
bond order A method of evaluating bond strength Molecular Orbitals
bonding electron pair A pair of electrons that makes a covalent bond Covalent Bonds
bonding molecular orbital The lower energy molecular orbital generated by constructive combination of atomic orbitals Molecular Orbitals
Boyle’s law A gas law that relates pressure and volume at constant temperature and amount Gas Laws
branched hydrocarbons A carbon compound that is not a straight chain, having substituents appended to the longest chain Branched Hydrocarbons
Brønsted-Lowry acid Any species that can donate a proton to another molecule Brønsted-Lowry Acids and Bases
Brønsted-Lowry base Any species that can accept a proton from another molecule Brønsted-Lowry Acids and Bases
buffer A solution that resists dramatic changes in pH Buffers
buffer capacity The amount of strong acid or base a buffer can counteract Buffers
burette or buret A precisely calibrated volumetric delivery tube Acid-Base Titrations
calorie A unit of energy measurement originally defined in terms of warming up a given quantity of water. 1 cal = 4.184 J Energy
calorimeter A container used to measure the heat of a chemical reaction Enthalpy and Chemical Reactions
calorimetry The process of measuring enthalpy changes for chemical reactions Enthalpy and Chemical Reactions
capillary action The behavior of a liquid in narrow surfaces due to differences in adhesion and cohesion Properties of Liquids
carbonyl group A functional group where an O atom and a C atom are joined with a double bond Other Oxygen-Containing Functional Groups
carboxyl group A functional group composed of a carbonyl group and an OH group Other Oxygen-Containing Functional Groups
carboxylate ion A negatively charged ion derived from a carboxylic acid Other Oxygen-Containing Functional Groups
carboxylic acid A molecule with a carboxyl group Other Oxygen-Containing Functional Groups
catalyst A substance that increases the speed of a reaction Shifting Equilibria: Le Chatelier’s Principle
catalyst A substance thaty accelerates a reaction by participating in it without being consumed Factors that Affect the Rate of Reactions
catalyst A substance that lowers the activation energy of a specific reaction by providing an alternate reaction pathway Catalysis
cathode The half cell that contains the reduction reaction Applications of Redox Reactions: Voltaic Cells
cation A species with an overall positive charge Ions and Ionic Compounds
central atom The atom in the center of a molecule Covalent Bonds
Charles’s law A gas law that relates volume and temperature at constant pressure and amount Gas Laws
chemical bond The connection between two atoms in a molecule Molecules an Chemical Nomenclature
chemical change The process of demonstrating a chemical property Some Basic Definitions
chemical equation A concise way of representing a chemical reaction The Chemical Equation
chemical equilibrium The point at which forward and reverse chemical reactions balance each other’s progress Chemical Equilibrium
chemical nomenclature A very specific system for naming compounds, in which unique substances get unique names Molecules an Chemical Nomenclature
chemical property A characteristic that describes how matter changes form in the presence of other matter Some Basic Definitions
chemistry The study of the interactions of matter with other matter and with energy Introduction
coefficient The part of a number in scientific notation that is multiplied by a power of 10 Expressing Numbers
coefficient A number in a chemical equation indicating more than one molecule of the substance The Chemical Equation
cohesion The tendency of a substance to interact with itself Properties of Liquids
colligative property A property of solutions related to the fraction that the solute particles occupy in the solution, not their identity Colligative Properties of Solutions
collision theory The theory that reactions occur when reactant molecules “effectively collide” Factors that Affect the Rate of Reactions
combined gas law A gas law that combines pressure, volume, and temperature Other Gas Laws
combustion reaction A chemical reaction in which a reactant combines with oxygen to produce oxides of all other elements as products Composition, Decomposition, and Combustion Reactions
complete ionic equation A chemical equation in which the dissolved ionic compounds are written as separated ions Ionic Equations: A Closer Look
composition reaction A chemical reaction in which a single substance is produced from multiple reactants Composition, Decomposition, and Combustion Reactions
compound A combination of more than one element Some Basic Definitions
compressibility factor A measure of the extent of deviation from ideal gas behaviour Real Gases
concentrated solution A solution with a lot of solute Some Definitions
concentration How much solute is dissolved in a given amount of solvent Some Definitions
concentration (verb) The removal of solvent, which increases the concentration of the solute in the solution Dilutions and Concentrations
condensation The process of a gas becoming a liquid Phase Transitions: Melting, Boiling and Subliming
condensed structure A listing of the atoms bonded to each C atom in a chain Hydrocarbons
conjugate acid-base pair Two species whose formulas differ by only a hydrogen ion Brønsted-Lowry Acids and Bases
continuous spectrum An image that contains all colors of light Quantum Numbers for Electrons
conversion factor A fraction that can be used to convert a quantity from one unit to another Converting Units
covalent bond A chemical bond formed by two atoms sharing electrons Covalent Bonds
covalent network solids A crystalline solid composed of atoms of one or more elements that are covalently bonded together in a seemingly never-ending fashion Solids
critical point The point at the highest temperature and pressure at which liquids and gases remain distinguishable Properties of Liquids
crystalline solid A solid with a regular, repeating three-dimensional structure Solids
curie A unit of radioactivity equal to 3.7×1010 decays/s Units of Radioactivity
d block The columns of the periodic table in which d subshells are being occupied Electronic Structure and the Periodic Table
Dalton’s law of partial pressures The total pressure of a gas mixture, Ptot, is equal to the sum of the partial pressures of the components, Pi Gas Mixtures
daughter isotope The product left over from the parent isotope in a nuclear equation Radioactivity
decomposition reaction A chemical reaction in which a single substance becomes more than one substance Composition, Decomposition, and Combustion Reactions
degrees The unit of temperature scales Other Units: Temperature and Density
density A physical property defined as a substance’s mass divided by its volume Other Units: Temperature and Density
deposition The process of a gas becoming a solid Phase Transitions: Melting, Boiling and Subliming
derived unit A unit that is a product or a quotient of a fundamental unit Expressing Units
diatomic molecule A molecule with only two atoms Molecules an Chemical Nomenclature
diffusion The movement of gas molecules through one or more additional types of gas via random molecular motion Molecular Effusion and Diffusion
dilute A solution with very little solute Some Definitions
dilution The addition of solvent, which decreases the concentration of the solute in the solution Dilutions and Concentrations
dilution equation The mathematical formula for calculating new concentrations or volumes when a solution is diluted or concentrated Dilutions and Concentrations
dipole-dipole interactions An intermolecular force caused by molecules with a permanent dipole Intermolecular Forces
dispersion force (or London dispersion force) An intermolecular force caused by the instantaneous position of an electron in a molecule Intermolecular Forces
dissociation The process of an ionic compound separating into ions when it dissolves Ionic Equations: A Closer Look
double bond A covalent bond composed of two pairs of bonding electrons Covalent Bonds
double-replacement reaction A chemical reaction in which parts of two ionic compounds are exchanged Types of Chemical Reactions: Single- and Double-Displacement Reactions
dry cell A modern battery that does not contain large amounts of aqueous solution Applications of Redox Reactions: Voltaic Cells
dynamic equilibrium When a process still occurs but the opposite process also occurs at the same rate so that there is no net change in the system. Properties of Liquids
effective nuclear charge (Zeff) The net nuclear charge feld by valence electrons Periodic Trends
effusion The movement of gas molecules from one container to another via a tiny hole Molecular Effusion and Diffusion
electrodes The cathode or anode of a voltaic cell Applications of Redox Reactions: Voltaic Cells
electrolysis The process of making a nonspontaneous redox reaction occur by forcing electricity into a cell Electrolysis
electrolytic cell A cell into which electricity is forced to make a nonspontaneous reaction occur Electrolysis
electromagnetic spectrum The full span of the possible wavelengths, frequencies, and energies of light Light
electron A tiny subatomic particle with a negative charge Atomic Theory
electron affinity (EA) The energy change when a gas-phase atom accepts an electron Periodic Trends
electron configuration A listing of the shell and subshells labels Organization of Electrons in Atoms
electron deficient molecules A molecule with less than eight electrons in the valence shell of an atom Violations of the Octet Rule
electron group geometry how electron groups (bonds and nonbonding electron pairs) are arranged Molecular Shapes and Polarity
electron groups A covalent bond of any type or a lone electron pair Molecular Shapes and Polarity
electron shell A term used to describe electrons with the same principal quantum number Quantum Numbers for Electrons
electronegativity A scale for judging how much atoms of any element attract electrons Other Aspects of Covalent Bonding
electroplating The deposition of a thin layer of metal on an object for protective or decorative purposes Electrolysis
element A substance that cannot be broken down into simpler chemical substances by ordinary chemical means Some Basic Definitions
elementary step Each event that occurs in a chemical reaction as a result of an effective collision Reaction Mechanisms
elimination reaction The removal of a functional group (either X or OH) and a H atom from an adjacent carbon Alkyl halides and alcohols
endothermic A chemical reaction that has a positive change in enthalpy Enthalpy and Chemical Reactions
energy The ability to do work. is the ability to do work Energy
enthalpy change The heat of a process at constant pressure; denoted ΔH Enthalpy and Chemical Reactions
enthalpy of formation The enthalpy change for a formation reaction; denoted ΔHf. and is given the symbol ΔHf Formation Reactions
enthalpy of fusion The amount of energy needed to change from a solid to a liquid or from a liquid to a solid Phase Transitions: Melting, Boiling and Subliming
enthalpy of sublimation The amount of energy needed to change from a solid to a gas or from a gas to a solid Phase Transitions: Melting, Boiling and Subliming
enthalpy of vaporization The amount of energy needed to change from a liquid to a gas or from a gas to a liquid Phase Transitions: Melting, Boiling and Subliming
entropy The level of randomness (or disorder) of a system, or a measure of the energy dispersal of the molecules in the system Entropy and the Second Law of Thermodynamics
enzyme Protein molecules which serve to catalyze biochemical reactions Catalysis
enzyme-substrate complex The binding of substrate to the enzymatic active site Catalysis
equilibrium constant (Keq) A numerical value that relates to the ratio of products and reactants at equilibrium The Equilibrium Constant
equivalence point The point of the reaction when all the analyte has been reacted with the titrant Acid-Base Titrations
ester group A functional group made by combining a carboxylic acid with an alcohol Other Oxygen-Containing Functional Groups
ether group A functional group that has an O atom attached to two organic groups Other Oxygen-Containing Functional Groups
evaporation The formation of a gas phase from a liquid at temperatures below the boiling point Properties of Liquids
exact number A number from a defined relationship that technically has an infinite number of significant figures Converting Units
exothermic A chemical reaction that has a negative change in enthalpy Enthalpy and Chemical Reactions
expanded valence shell molecules A molecule with more than eight electrons in the valence shell of an atom Violations of the Octet Rule
experiment A test of the natural universe to see if a guess (hypothesis) is correct Chemistry as a Science
exponent The raised number to the right of a 10 indicating the number of factors of 10 in the original number Expressing Numbers
f block The columns of the periodic table in which f subshells are being occupied Electronic Structure and the Periodic Table
fission The breaking apart of an atomic nucleus into smaller nuclei Radioactivity
formation reaction A chemical reaction that forms one mole of a substance from its constituent elements in their standard states Formation Reactions
freezing point depression The decrease of a solution’s freezing point because of the presence of solute Colligative Properties of Solutions
freezing point depression constant (Kf) The constant that relates the molality concentration of a solution and its freezing point change Colligative Properties of Solutions
frequency The number of cycles of light that pass a given point in one second Light
frequency factor (A) A factor that takes into account the frequency of reactions and the likelihood of correct molecular orientation Activation Energy and the Arrhenius Equation
frontier molecular orbitals A term which refers to the HOMO and LUMO, the most likely orbitals to be involved in chemical reactions or processes Molecular Orbitals
functional group A collection of atoms or bonds with certain characteristic reactions Alkyl halides and alcohols
fundamental units One of the seven basic units of SI used in science Expressing Units
gamma ray A type of radioactive emission that is a very energetic form of electromagnetic radiation Radioactivity
gas law A simple mathematical formula that allows one to model, or predict, the behavior of a gas Gas Laws
Gay-Lussac’s law A gas law that relates pressure with absolute temperature Other Gas Laws
Geiger counter An electrical device that detects radioactivity Units of Radioactivity
Gibbs free energy (G) A measure of spontaneity which incorporates both enthalpy and entropy Gibbs Free Energy
Graham’s law of effusion A law which relates the rate of effusion of a gas to the inverse of the square root of its molar mass Molecular Effusion and Diffusion
gray (Gy) A unit of radioactive exposure qual to 100 rad Units of Radioactivity
half cell A part of a voltaic cell that contains one half reaction Applications of Redox Reactions: Voltaic Cells
half reaction The individual oxidation or reduction reaction of a redox reaction Balancing Redox Reactions
half reaction method The method of balancing redox reactions by writing and balancing the individual half reactions Balancing Redox Reactions
half-life The amount of time it takes for one-half of a radioactive isotope to decay Half-Life
half-life The amount of time required for the concentration of a reactant to drop to one half of its initial concentration Concentration-Time Relationships: Integrated Rate Laws
heat The transfer of energy from one body to another due to a difference in temperature Work and Heat
heating curve A plot of the temperature versus the amount of heat added Phase Transitions: Melting, Boiling and Subliming
Hess’s law When chemical equations are combined algebraically, their enthalpies can be combined in exactly the same way Hess’s Law
heterogeneous catalyst A catalyst that is in a different phase from one or more of the reactants Catalysis
heterogeneous equilibrium An equilibrium in which more than one phase of reactants or products is present The Equilibrium Constant
heterogeneous mixture A non-uniform combination of more than one substance Some Basic Definitions
HOMO The highest occupied molecular orbital Molecular Orbitals
homogeneous catalyst A catalyst that is present in the same phase as the reactant molecules Catalysis
homogeneous mixture A uniform mixture of more than one substance that behaves as a single substance Some Basic Definitions
Hund’s rule One electron is placed in each degenerate orbital before pairing electrons in the same orbital Organization of Electrons in Atoms
hybridization A mathematical mixing of atomic orbitals Valence Bond Theory and Hybrid Orbitals
hydrocarbons An organic compound composed of carbon and hydrogen Hydrocarbons
hydrogen bonding The very strong interaction between molecules due to H atoms being bonded to N, O, or F atoms Intermolecular Forces
hydrogenation reaction The reaction of hydrogen across a C–C double or triple bond, usually in the presence of a catalyst Hydrocarbons
hydronium ion The actual chemical species that represents a hydrogen ion in aqueous solution Arrhenius Acids and Bases
hypothesis An educated guess about how the natural universe works Chemistry as a Science
hyrolysis A reaction with water Brønsted-Lowry Acids and Bases
ICE chart A table used to calculate equilibria values featuring rows of initial, change and equlibria concentration Calculating Equilibrium Constant Values
ideal gas A gas that conforms exactly to the tenets of the kinetic molecular theory Real Gases
ideal gas law A gas law that relates all four independent physical properties of a gas under any conditions The Ideal Gas Law and Some Applications
indicator A substance whose color change indicates the equivalence point of a titration Acid-Base Titrations
initial rate The instantaneous rate at the start of a reaction Reaction Rates
initial rates method A method to determine the rate law from the instantaneous reaction rate upon mixing the reactants Rate Laws
instantaneous reaction rate The rate of reaction at one instant in time Reaction Rates
intermediate A chemical species does not appear in the overall balanced equation and is generated in one elementary step but used up in a subsequent step Reaction Mechanisms
ion A species with an overall electric charge Ions and Ionic Compounds
ionic compound A compound formed from positive and negative ions Ions and Ionic Compounds
ionic formula The chemical formula for an ionic compound Ions and Ionic Compounds
ionic solid A crystalline solid composed of ions Solids
ionization energy (IE) The amount of energy required to remove an elec tron from an atom in the gas phase Periodic Trends
isolated system A system that does not allow a transfer of energy or matter into or out of the system Energy
isomer A molecule with the same molecular formula as another molecule but a different structure Hydrocarbons
isothermal A process that does not change the temperature Phase Transitions: Melting, Boiling and Subliming
isotopes Atoms of the same element that have different numbers of neutrons Atomic Theory
joule The SI unit of energy Energy
Kelvin scale The fundamental unit of temperature in SI Other Units: Temperature and Density
ketone A compound where the carbonyl carbon is attached to two carbon chains Other Oxygen-Containing Functional Groups
kinetic energy The energy due to motion Kinetic-Molecular Theory of Gases
kinetic-molecular theory of gases A model which helps us understand gases at the molecular level and their physical properties Kinetic-Molecular Theory of Gases
kinetics The study of reaction rate and the factors that can influence reaction rate Introduction to Kinetics
law of conservation of energy The total energy of an isolated system does not increase or decrease Energy
law of mass action The relationship of the amounts of reactants and products at equilibrium The Equilibrium Constant
Le Chatelier’s principle If an equilibrium is stressed, then the reaction shifts to reduce the stress Shifting Equilibria: Le Chatelier’s Principle
Lewis diagram A representation of the valence electrons of an atom that uses dots around the symbol of the element Lewis Electron Dot Diagrams
limiting reagent The reactant that runs out first for a given chemical reaction Limiting Reagents
line spectrum An image that contains only certain colors of light Quantum Numbers for Electrons
locant The numerical position of a substituent Branched Hydrocarbons
lock and key model A simple model used to describe enzyme activity, where substrates must fit into appropriately shaped active sites Catalysis
lone electron pairs A pair of electrons that does not make a covalent bond Covalent Bonds
LUMO The lowest unoccupied molecular orbital Molecular Orbitals
magnetic quantum number (ml) The index that determines the orientation of the electron’s spatial distribution Quantum Numbers for Electrons
mass-mass calculation A calculation in which you start with a given mass of a substance and calculate the mass of another substance involved in the chemical equation Mole-Mass and Mass-Mass Calculations
matter Anything that has mass and takes up space. is anything that has mass and takes up space Some Basic Definitions
mean free path The average distance traveled by a molecule between collisions Molecular Effusion and Diffusion
melting The process of a solid becoming a liquid Phase Transitions: Melting, Boiling and Subliming
melting point The characteristic temperature at which a solid becomes a liquid Phase Transitions: Melting, Boiling and Subliming
meniscus The curved surface a liquid makes as it approaches a solid barrier Properties of Liquids
metal An element that conducts electricity and heat well and is shiny, silvery, solid, ductile, and malleable Some Basic Definitions
metallic solid A solid with the characteristic properties of a metal Solids
microstate (W) A term used to describe different possible arrangements of molecular position and kinetic energy, at a particular thermodynamic state Entropy and the Second Law of Thermodynamics
millimeters of mercury (mmHg) The amount of pressure exerted by a column of mercury exactly 1 mm high Pressure
mixture A physical combination of more than one substance Some Basic Definitions
molality (m) The number of moles of solute per kilogram of solvent Quantitative Units of Concentration
molar mass The mass of 1 mol of a substance in grams The Mole
molar volume The volume of exactly 1 mol of a gas; equal to 22.4 L at STP The Ideal Gas Law and Some Applications
molarity (M) The number of moles of solute divided by the number of liters of solution Quantitative Units of Concentration
mole The number of things equal to the number of atoms in exactly 12 g of carbon-12; equals 6.022×1023 things The Mole
mole fraction The ratio of the number of moles of a component in a mixture divided by the total number of moles in the sample Gas Mixtures
mole fraction The ratio of the number of moles of a component to the total number of moles in a system Colligative Properties of Solutions
molecular formula A formal listing of what and how many atoms are in a molecule Molecules an Chemical Nomenclature
molecular geometry how the atoms in a molecule are arranged Molecular Shapes and Polarity
molecular mass The sum of the masses of the atoms in a molecule Masses of Atoms and Molecules
molecular orbital theory (MO theory) A more sophisticated model  of chemical bonding where new molecular orbitals are generated using a mathematical process called Linear Combination of Atomic Orbitals (LCAO) Molecular Orbitals
molecular polarity The vector sum of the individual bond dipoles Molecular Shapes and Polarity
molecular solid A crystalline solid whose components are covalently bonded molecules Solids
molecularity The total number of molecules that participate in the effective collision of the elementary step Reaction Mechanisms
molecule The smallest part of a substance that has the physical and chemical properties of that substance Molecules an Chemical Nomenclature
mole-mass calculation A calculation in which you start with a given number of moles of a substance and calculate the mass of another substance involved in the chemical equation, or vice versa Mole-Mass and Mass-Mass Calculations
mole-mole calculation A stoichiometry calculation when one starts with moles of one substance and convert to moles of another substance using the balanced chemical equation The Mole in Chemical Reactions
monomer The repeated unit of a polymer Polymers
net ionic equation A chemical equation with the spectator ions removed Ionic Equations: A Closer Look
neutral salt An ionic compound that does not affect the acidity of its aqueous solution Strong and Weak Acids and Bases and Their Salts
neutralization reaction The reaction of an acid with a base to produce water and a salt Neutralization Reactions
neutralization reaction The reaction of an acid and a base to produce water and a salt Arrhenius Acids and Bases
neutron A subatomic particle with no charge Atomic Theory
node (nodal plane) An area of zero electron density Molecular Orbitals
nomenclature The rules of naming in organic chemistry Branched Hydrocarbons
nonmetal An element that exists in various colors and phases, is brittle, and does not conduct electricity or heat well Some Basic Definitions
nonpolar covalent bond The equal sharing of electrons in a covalent bond Other Aspects of Covalent Bonding
normal boiling point The characteristic temperature at which a liquid becomes a gas when the surrounding pressure is exactly 1 atm Phase Transitions: Melting, Boiling and Subliming
nuclear energy The controlled harvesting of energy from fission reactions Nuclear Energy
nuclear equation A chemical equation that emphasizes changes in atomic nuclei Radioactivity
nuclear model The model of an atom that has the protons and neutrons in a central nucleus with the electrons in orbit about the nucleus Atomic Theory
nucleus The center of an atom that contains protons and neutrons Atomic Theory
odd-electron molecules A molecule with an odd number of electrons in the valence shell of an atom Violations of the Octet Rule
orbital The specific set of principal, angular momentum, and magnetic quantum numbers for an electron Quantum Numbers for Electrons
osmosis The tendency of solvent molecules to pass through a semipermeable membrane due to concentration differences Colligative Properties of Solutions
osmotic pressure The tendency of a solution to pass solvent through a semipermeable membrane due to concentration differences Colligative Properties of Solutions
oxidation The loss of one or more electrons by an atom; an increase in oxidation number Oxidation-Reduction Reactions
oxidation The loss of one or more electrons by an atom; an increase in oxidation number Oxidation-Reduction Reactions
oxidation number A number assigned to an atom that helps keep track of the number of electrons on the atom Oxidation-Reduction Reactions
oxidation number A number assigned to an atom that helps keep track of the number of electrons on the atom Oxidation-Reduction Reactions
oxidation-reduction (redox) reactions A chemical reaction that involves the transfer of electrons Oxidation-Reduction Reactions
p block The columns of the periodic table in which p subshells are being occupied Electronic Structure and the Periodic Table
parent isotope The reactant in a nuclear equation Radioactivity
parts per billion (ppb) Ratio of mass of solute to total mass of sample times 1,000,000,000 Quantitative Units of Concentration
parts per million (ppm) Ratio of mass of solute to total mass of sample times 1,000,000 Quantitative Units of Concentration
parts per thousand (ppth) Ratio of mass of solute to total mass of sample times 1,000 Quantitative Units of Concentration
Pauli exclusion principle No two electrons in an atom can have the same set of four quantum numbers Organization of Electrons in Atoms
percent yield Actual yield divided by theoretical yield times 100% to give a percentage between 0% and 100% Yields
percentage composition by mass (or mass percentage, % m/m) Ratio of mass of solute to the total mass of a sample times 100 Quantitative Units of Concentration
periodic table A chart of all the elements Atomic Theory
periodic trends The variation of properties versus position on the periodic table Periodic Trends
pH The negative logarithm of the hydrogen ion concentration The pH Scale
pH scale The range of values from 0 to 14 that describes the acidity or basicity of a solution The pH Scale
phase An important physical property that defines whether matter is a solid, liquid, gas or supercritical fluid Some Basic Definitions
phase diagram A graphical representation of the equilibrium relationships that exist between the phases of a substance under specified pressures and temperatures Properties of Liquids
photon The name of a discrete unit of light acting as a particle Light
physical change A change that occurs when a sample of matter changes one or more of its physical properties Some Basic Definitions
physical property A characteristic that describes matter as it exists Some Basic Definitions
pi bond (π bond) The sideways overlap of p orbitals, placing electron density on opposite sides of the inter-nuclear axis – a double or triple bond Valence Bond Theory and Hybrid Orbitals
Planck’s constant The proportionality constant between the frequency and the energy of light: 6.626 × 10−34 J·s Light
pOH The negative logarithm of the hydroxide ion concentration The pH Scale
polar covalent bond A covalent bond between different atoms that attract the shared electrons by different amounts and cause an imbalance of electron distribution Other Aspects of Covalent Bonding
polarity A measure of the unequal sharing of electrons which has resulted in a dipole moment Other Aspects of Covalent Bonding
polyatomic ions An ion that contains more than one atom Ions and Ionic Compounds
polymer A long molecule made of many repeating units Polymers
polymerization The process of making a polymer Polymers
polyprotic acid An acid capable of donating more than one H+ ion Some Special Types of Equilibria
precipitate A solid that falls out of solution in a precipitation reaction Types of Chemical Reactions: Single- and Double-Displacement Reactions
precipitation reaction A chemical reaction in which two ionic compounds are dissolved in water and form a new ionic compound that does not dissolve Types of Chemical Reactions: Single- and Double-Displacement Reactions
prefix A prefix used with a unit that refers to a multiple or fraction of a fundamental unit to make a more conveniently sized unit for a specific quantity Expressing Units
pressure Force per unit area Pressure
primary battery A battery that cannot be recharged Applications of Redox Reactions: Voltaic Cells
principal quantum number (n) The index that largely determines the energy of an electron in an atom Quantum Numbers for Electrons
product A final substance in a chemical equation The Chemical Equation
proton A subatomic particle with a positive charge Atomic Theory
qualitative A description of the quality of an object Chemistry as a Science
quantitative A description of a specific amount of something Chemistry as a Science
quantization When a quantity is restricted to having only certain values Quantum Numbers for Electrons
quantum mechanics The theory of electrons that treats them as a wave Quantum Numbers for Electrons
quantum number An index that corresponds to a property of an electron, like its energy Quantum Numbers for Electrons
rad A unit of radioactive exposure equal to 0.01 J/g of tissue Units of Radioactivity
radioactive decay The spontaneous change of a nucleus from one element to another Radioactivity
radioactivity Emanations of particles and radiation from atomic nuclei Radioactivity
Raoult’s law The mathematical formula for calculating the vapor pressure of a solution Colligative Properties of Solutions
rate constant (k) A proportionality constant specific to each reaction at a particular temperature Rate Laws
rate-determining step The slowest step in a multistep mechanism Reaction Mechanisms
rate law A mathematical relationship between the reaction rate and the reactant concentrations Rate Laws
reactant An initial substance in a chemical equation The Chemical Equation
reaction mechanism The bond making and bond breaking steps which occur at the molecular level during a chemical reaction Reaction Mechanisms
reaction order The sum of the concentration term exponents in a rate law equation Rate Laws
reaction rate The speed of a chemical reaction Introduction to Kinetics
real gases A gas that deviates from ideal behaviour Real Gases
redox reaction A chemical reaction that involves the transfer of electrons Oxidation-Reduction Reactions
reduction The gain of one or more electrons by an atom; a decrease in oxidation number Oxidation-Reduction Reactions
reduction The gain of one or more electrons by an atom; a decrease in oxidation number Oxidation-Reduction Reactions
rem A unit of radioactive exposure that includes a factor to account for the type of radioactivity Units of Radioactivity
ribozyme Ribonucleic acid (RNA) molecules capable of catalyzing certain chemical reactions Catalysis
root-mean-square (rms) speed (urms) The speed of molecules having exactly the same kinetic energy as the average kinetic energy of the sample Kinetic-Molecular Theory of Gases
s block The columns of the periodic table in which s subshells are being occupied Electronic Structure and the Periodic Table
salt Any ionic compound that is formed from a reaction between an acid and a base Neutralization Reactions
salt Any ionic compound that is formed from a reaction between an acid and a base Arrhenius Acids and Bases
salt bridge A part of a voltaic cell that contains a solution of some ionic compound whose ions migrate to either side of the voltaic cell to maintain the charge balance Applications of Redox Reactions: Voltaic Cells
saturated hydrocarbons A carbon compound with the maximum possible number of H atoms in its formula Hydrocarbons
saturated solution A solution with the maximum amount of solute dissolved in it Some Definitions
science The process of knowing about the natural universe through observation and experiment Chemistry as a Science
scientific law A specific statement that is thought to be never violated by the entire natural universe Chemistry as a Science
scientific notation An expression of a number using powers of 10 Expressing Numbers
screening The repelling valence electrons by core electrons Periodic Trends
second law of thermodynamics A spontaneous process will increase the entropy of the universe Entropy and the Second Law of Thermodynamics
secondary battery A battery that can be recharged Applications of Redox Reactions: Voltaic Cells
semimetal An element that has properties of both metals and nonmetals Some Basic Definitions
semipermeable membrane A thin membrane that will pass certain small molecules but not others Colligative Properties of Solutions
SI unit  International System of Units used by all scientists, literally translated from “le Système International d’unités.” Expressing Units
Sievert (Sv) Sievert (Sv) is a related unit and is defined as 100 rem Units of Radioactivity
sigma bond (σ bond) Orbital overlap to form a bond which has cylindrical symmetry – a single bond Valence Bond Theory and Hybrid Orbitals
significant figures The limit of the number of places a measurement can be properly expressed with Significant Figures
silicones A polymer based on a silicon and oxygen backbone Polymers
single bond A covalent bond composed of one pair of electrons Covalent Bonds
single-replacement reaction A chemical reaction in which one element is substituted for another element in a compound Types of Chemical Reactions: Single- and Double-Displacement Reactions
solidification The process of a liquid becoming a solid Phase Transitions: Melting, Boiling and Subliming
solubility The maximum amount of a solute that can be dissolved in a given amount of a solvent Some Definitions
solubility rules General statements that predict which ionic compounds dissolve and which do not Types of Chemical Reactions: Single- and Double-Displacement Reactions
solute The minor component of a solution Some Definitions
solution See homogeneous mixture Some Basic Definitions
solvent The major component of a solution Some Definitions
specific heat capacity The proportionality constant between heat, mass, and temperature change; also called specific heat Work and Heat
spectator ion An ion that does nothing in the overall course of a chemical reaction Ionic Equations: A Closer Look
spin quantum number (ms) The index that indicates one of two spin states for an electron Quantum Numbers for Electrons
spontaneous process A process that occurs without the influence of external forces or a change that moves a system towards equilibrium Spontaneous Change
standard molar entropy  (So) The entropy of 1 mole of a substance in its standard state, at 1 atm of pressure Measuring Entropy and Entropy Changes
standard notation A straightforward expression of a number Expressing Numbers
standard temperature and pressure (STP) A set of benchmark conditions used to compare other properties of gases; 100 kPa for pressure and 273 K for temperature The Ideal Gas Law and Some Applications
stoichiometry The relating of one chemical substance to another using a balanced chemical reaction Stoichiometry
strong acid Any acid that is 100% dissociated into ions in aqueous solution Strong and Weak Acids and Bases and Their Salts
strong base Any base that is 100% dissociated into ions in aqueous solution Strong and Weak Acids and Bases and Their Salts
sublimation The process of a solid becoming a gas Phase Transitions: Melting, Boiling and Subliming
subshell A term used to describe electrons in a shell that have the same angular momentum quantum number Quantum Numbers for Electrons
substance Matter that has the same physical and chemical properties throughout. Some Basic Definitions
substituent A branch off a main chain in a hydrocarbon Branched Hydrocarbons
substrate The reactants which are specific for a biological catalyst Catalysis
supercritical fluid A phase beyond the critical point, where liquid and gas phases are no longer distinct Properties of Liquids
supersaturated solution A unstable solution with more than the normal maximum amount of solute in it Some Definitions
surface tension An effect caused by an imbalance of forces on the atoms at the surface of a liquid Properties of Liquids
surrounding atoms An atom that makes covalent bonds to the central atom(s) Covalent Bonds
system The part of the universe under study Energy
temperature A measure of the average amount of kinetic energy a system contains Other Units: Temperature and Density
theoretical yield An amount that is theoretically produced as calculated using the balanced chemical reaction Yields
theory A general statement that explains a large number of observations Chemistry as a Science
thermochemical equation A chemical equation that includes an enthalpy change Enthalpy and Chemical Reactions
thiol The sulfur analog of an alcohol Other Functional Groups
third law of thermodynamics At absolute zero the entropy of a pure, perfect crystal is zero Measuring Entropy and Entropy Changes
titrant The reagent of known concentration Acid-Base Titrations
titration A chemical reaction performed quantitatively to determine the exact amount of a reagent Acid-Base Titrations
torr Another name for a millimeter of mercury Pressure
tracer A substance that can be used to follow the pathway of that substance through a structure Uses of Radioactive Isotopes
transition state The highest energy transitional point in the elementary step Reaction Mechanisms
triple bond A covalent bond composed of three pairs of bonding electrons Covalent Bonds
unsaturated hydrocarbons A carbon compound with less than the maximum possible number of H atoms in its formula Hydrocarbons
unsaturated solution A solution with less than the maximum amount of solute dissolved in it Some Definitions
valence electrons The electrons in the highest-numbered shell, plus any electrons in the last unfilled subshell. The electrons most likely involved in chemical reactions Electronic Structure and the Periodic Table
valence shell The highest-numbered shell in an atom that contains electrons Electronic Structure and the Periodic Table
valence shell electron pair repulsion theory (VSEPR) The general concept that estimates the shape of a simple molecule:  electron pairs repel each other to get as far away from each other as possible Molecular Shapes and Polarity
van der Waal’s equation An equation which compensates for deviations from ideal gas behaviour, correcting for intermolecular forces and the volume of gas molecules Real Gases
van’t Hoff factor (i) The number of particles each solute formula unit breaks apart into when it dissolves Colligative Properties of Ionic Solutes
vapor Material in the gas phase due to evaporation Properties of Liquids
vapor pressure The partial pressure exerted by evaporation of a liquid Gas Mixtures
vapor pressure depression The decrease of a solution’s vapor pressure because of the presence of a solute Colligative Properties of Solutions
vector quantity A quantity which has both a magnitude and direction Molecular Shapes and Polarity
voltaic (galvanic) cell An apparatus that allows for useful electrical work to be extracted from a redox reaction. Applications of Redox Reactions: Voltaic Cells
wavelength The distance between corresponding points in two adjacent light cycles Light
weak acid Any acid that is less than 100% dissociated into ions in aqueous solution Strong and Weak Acids and Bases and Their Salts
weak base Any base that is less than 100% dissociated into ions in aqueous solution Strong and Weak Acids and Bases and Their Salts

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Glossary by Jessie A. Key is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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