Glossary
- abbreviated electron configuration
-
An electron configuration that uses one of the noble gases to represent the core of electrons up to that element.
- absolute zero
-
The minimum possible temperature, labelled 0 K (zero kelvins).
- acid
-
An ionic compound of the H+ cation dissolved in water.
- activity series
-
A list of elements that will replace elements below them in single-replacement reactions.
- actual yield
-
The amount that is actually produced in a chemical reaction.
- angular momentum quantum number (ℓ)
-
An index that affects the energy and the spatial distribution of an electron in an atom.
- anion
-
A species with an overall negative charge.
- atmosphere (atm)
-
A unit of pressure equal to the average atmospheric pressure at sea level; defined as exactly 760 mmHg.
- atom
-
The smallest piece of an element that maintains the identity of that element.
- atomic mass
-
The weighted average of the masses of the isotopes that compose an element.
- atomic mass unit
-
One-twelfth of the mass of a carbon-12 atom.
- atomic number
-
The number of protons in an atom.
- atomic radius
-
An indication of the size of an atom.
- atomic symbol
-
A one- or two-letter representation of the name of an element.
- atomic theory
-
The concept that atoms play a fundamental role in chemistry.
- aufbau principle
-
The way that electrons fill the lowest energy orbitals first. From the German for "building up."
- Avogadro’s law
-
A gas law that relates number of particles to volume.
- balanced chemical equation
-
A condition when the reactants and products of a chemical equation have the same number of atoms of all elements present.
- base
-
A compound that increases the amount of OH− ions in an aqueous solution.
- Boyle’s law
-
A gas law that relates pressure and volume at constant temperature and amount.
- calorie
-
A unit of energy measurement originally defined in terms of warming up a given quantity of water. 1 cal = 4.184 J
- calorimeter
-
A container used to measure the heat of a chemical reaction.
- calorimetry
-
The process of measuring enthalpy changes in chemical reactions.
- cation
-
A species with an overall positive charge.
- Charles’s law
-
A gas law that relates volume and temperature at constant pressure and amount.
- chemical change
-
The process of demonstrating a chemical property.
- chemical equation
-
A concise way of representing a chemical reaction.
- chemical property
-
A characteristic that describes how matter changes form in the presence of other matter.
- chemistry
-
The study of the interactions of matter with other matter and with energy.
- coefficient
-
The raised number to the right of a 10 indicating the number of factors of 10 in the original number.
- combined gas law
-
A gas law that combines pressure, volume, and temperature.
- complete ionic equation
-
A chemical equation in which the dissolved ionic compounds are written as separated ions.
- composition reaction
-
A chemical reaction in which a single substance is produced from multiple reactants.
- compound
-
A combination of more than one element.
- compressibility factor
-
A measure of the extent of deviation from ideal gas behaviour.
- continuous spectrum
-
An image that contains all colours of light.
- conversion factor
-
A fraction that can be used to convert a quantity from one unit to another.
- covalent bond
-
A chemical bond formed by two atoms sharing electrons.
- d block
-
The columns of the periodic table in which d subshells are being occupied.
- Dalton’s law of partial pressures
-
The total pressure of a gas mixture, P_tot, is equal to the sum of the partial pressures of the components, P_i.
- decomposition reaction
-
A chemical reaction in which a single substance becomes more than one substance.
- degrees
-
The unit of temperature scales.
- derived unit
-
A unit that is a product or a quotient of a fundamental unit.
- diffusion
-
The movement of gas molecules through one or more additional types of gas via random molecular motion.
- double-replacement reaction
-
A chemical reaction in which parts of two ionic compounds are exchanged.
- effective nuclear charge
-
The net nuclear charge felt by valence electrons. Denoted as Z_eff ("zed-effective").
- effusion
-
The movement of gas molecules from one container to another via a tiny hole.
- electromagnetic spectrum
-
The full span of the possible wavelengths, frequencies, and energies of light.
- electron
-
A tiny subatomic particle with a negative charge.
- electron affinity (EA)
-
The energy change when a gas-phase atom accepts an electron.
- electron configuration
-
A listing of the shell and subshell labels.
- electron shell
-
A term used to describe electrons with the same principal quantum number.
- element
-
A substance that cannot be broken down into simpler chemical substances by ordinary chemical means.
- endothermic
-
A chemical reaction that has a positive change in enthalpy.
- energy
-
The ability to do work.
- enthalpy change
-
The heat of a process at constant pressure. Denoted as ΔH.
- enthalpy of formation
-
The enthalpy change for a formation reaction; denoted as ΔHf.
- exact number
-
A number from a defined relationship that technically has an infinite number of significant figures.
- exothermic
-
A chemical reaction that has a negative change in enthalpy.
- experiment
-
A test of the natural universe to see if a guess (hypothesis) is correct.
- exponent
-
The raised number to the right of a 10 indicating the number of factors of 10 in the original number.
- f block
-
The columns of the periodic table in which f subshells are being occupied.
- formation reaction
-
A chemical reaction that forms one mole of a substance from its constituent elements in their standard states.
- frequency
-
The number of cycles of light that pass a given point in one second.
- fundamental units
-
One of the seven basic units of SI used in science.
- gas law
-
A simple mathematical formula that allows one to model, or predict, the behaviour of a gas.
- Gay-Lussac’s law
-
A gas law that relates pressure with absolute temperature.
- Graham’s law of effusion
-
A law that relates the rate of effusion of a gas to the inverse of the square root of its molar mass.
- heat
-
The transfer of energy from one body to another due to a difference in temperature.
- Hess’s law
-
When chemical equations are combined algebraically, their enthalpies can be combined in exactly the same way.
- heterogeneous mixture
-
A non-uniform combination of more than one substance.
- homogeneous mixture
-
A uniform mixture of more than one substance that behaves as a single substance.
- Hund’s rule
-
One electron is placed in each degenerate orbital before pairing electrons in the same orbital.
- hydronium ion
-
The actual chemical species that represents a hydrogen ion in aqueous solution.
- hypothesis
-
An educated guess about how the natural universe works.
- ideal gas
-
A gas that conforms exactly to the tenets of the kinetic molecular theory.
- ideal gas law
-
A gas law that relates all four independent physical properties of a gas under any conditions.
- ion
-
A species with an overall electric charge.
- ionic bond
-
The attraction between oppositely charged ions.
- ionic compound
-
A compound formed from positive and negative ions.
- ionization energy (IE)
-
The amount of energy required to remove an electron from an atom in the gas phase.
- isolated system
-
A system that does not allow a transfer of energy or matter into or out of itself.
- isotopes
-
Atoms of the same element that have different numbers of neutrons.
- joule
-
The SI unit of energy.
- kelvin
-
The fundamental unit of temperature in SI.
- kinetic energy
-
Energy due to motion.
- kinetic molecular theory of gases
-
A model that helps us understand gases and their physical properties at the molecular level.
- lattice energy
-
The measured strength of ionic bonding.
- law of conservation of energy
-
Law of physics that states that the total energy of an isolated system does not increase or decrease.
- Lewis diagram
-
A representation of the valence electrons of an atom that uses dots around the symbol of the element.
- limiting reagent
-
The reactant that runs out first for a given chemical reaction.
- magnetic quantum number (mℓ)
-
The index that determines the orientation of the electron’s spatial distribution.
- mass number
-
The sum of the number of protons and neutrons in a nucleus.
- 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.
- matter
-
Anything that has mass and takes up space.
- mean free path
-
The average distance travelled by a molecule between collisions.
- metal
-
An element that conducts electricity and heat well and is shiny, silvery, solid, ductile, and malleable.
- millimetre of mercury (mmHg)
-
The amount of pressure exerted by a column of mercury exactly 1 mm high. Approximately 1 mmHg is equal to 1 torr.
- mixture
-
A physical combination of more than one substance.
- molar mass
-
The mass of 1 mol of a substance in grams.
- molar volume
-
The volume of exactly 1 mol of a gas; equal to 22.4 L at STP.
- mole
-
The number of things equal to the number of atoms in exactly 12 g of carbon-12; equals 6.022 × 10 to the power of 23 things.
- mole fraction
-
The ratio of the number of moles of a component to the total number of moles in a system.
- 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-mole calculation
-
A stoichiometry calculation in which one starts with moles of one substance and converts to moles of another substance using the balanced chemical equation.
- molecular mass
-
The sum of the masses of the atoms in a molecule.
- net ionic equation
-
A chemical equation with the spectator ions removed.
- neutralization reaction
-
The reaction of an acid with a base to produce water and a salt.
- neutron
-
A subatomic particle with no charge.
- nonmetal
-
An element that exists in various colors and phases, is brittle, and does not conduct electricity or heat well.
- 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.
- nucleus
-
The centre of an atom that contains protons and neutrons.
- numerical 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.
- octet rule
-
The trend that atoms like to have eight electrons in their valence shell.
- orbital
-
The specific set of principal, angular momentum, and magnetic quantum numbers for an electron.
- oxidation
-
The loss of one or more electrons by an atom; an increase in oxidation number.
- oxidation number
-
A number assigned to an atom that helps keep track of the number of electrons on the atom.
- oxidation-reduction (redox) reactions
-
A chemical reaction that involves the transfer of electrons.
- p block
-
The columns of the periodic table in which p subshells are being occupied.
- partial pressure
-
The pressure that an individual gas in a mixture has.
- Pauli exclusion principle
-
No two electrons in an atom can have the same set of four quantum numbers.
- percent yield
-
Actual yield divided by theoretical yield times 100%, which gives a percentage between 0% and 100%.
- periodic table
-
A chart of all the elements.
- periodic trends
-
The variation of properties versus position on the periodic table.
- phase
-
An important physical property that defines whether matter is a solid, liquid, gas or supercritical fluid. Also known as a state.
- photon
-
The name of a discrete unit of light acting as a particle.
- physical change
-
A change that occurs when a sample of matter changes one or more of its physical properties.
- physical property
-
A characteristic that describes matter as it exists.
- Planck’s constant
-
The proportionality constant between the frequency and the energy of light: 6.626 × 10 to the power of −34 J·s.
- precipitate
-
A solid that falls out of solution in a precipitation reaction.
- precipitation reaction
-
A chemical reaction in which two ionic compounds are dissolved in water and form a new ionic compound that does not dissolve.
- pressure
-
Force per unit area.
- principal quantum number (n)
-
The index that largely determines the energy of an electron in an atom.
- product
-
A final substance in a chemical equation.
- proton
-
A subatomic particle with a positive charge.
- qualitative
-
A description of the quality of an object.
- quantitative
-
A description of a specific amount of something.
- quantization
-
When a quantity is restricted to having only certain values.
- quantum mechanics
-
The theory of electrons that treats them as a wave.
- quantum number
-
An index that corresponds to a property of an electron, like its energy.
- reactant
-
An initial substance in a chemical equation.
- real gas
-
A gas that deviates from ideal behaviour.
- reduction
-
The gain of one or more electrons by an atom; a decrease in oxidation number.
- root-mean-square (rms) speed
-
The speed of molecules having exactly the same kinetic energy as the average kinetic energy of the sample.
- s block
-
The columns of the periodic table in which s subshells are being occupied.
- science
-
The process of knowing about the natural universe through observation and experiment.
- scientific notation
-
An expression of a number using powers of 10.
- semimetal
-
An element that has properties of both metals and nonmetals.
- significant figures
-
The limit of the number of places a measurement can be properly expressed with.
- single-replacement reaction
-
A chemical reaction in which one element is substituted for another element in a compound.
- solubility rules
-
General statements that predict which ionic compounds dissolve and which do not.
- specific heat capacity
-
The proportionality constant between heat, mass, and temperature change; also called specific heat.
- spectator ion
-
An ion that does nothing in the overall course of a chemical reaction.
- spin quantum number
-
The index that indicates one of two spin states for an electron.
- standard notation
-
A straightforward expression of a number.
- 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.
- stoichiometry
-
The relating of one chemical substance to another using a balanced chemical reaction.
- subshell
-
A term used to describe electrons in a shell that have the same angular momentum quantum number.
- substance
-
Matter that has the same physical and chemical properties throughout.
- system
-
The part of the universe that is under study.
- temperature
-
A measure of the average amount of kinetic energy a system contains.
- theoretical yield
-
An amount that is theoretically produced as calculated using the balanced chemical reaction.
- theory
-
A general statement that explains a large number of observations.
- thermochemical equation
-
A chemical equation that includes an enthalpy change.
- valence electron
-
An electron in the highest-numbered shell or in the last unfilled subshell. Valence electrons are those that are most likely to be involved in chemical reactions.
- valence shell
-
The highest-numbered shell in an atom that contains electrons.
- van der Waals equation
-
An equation that compensates for deviations from ideal gas behaviour, correcting for intermolecular forces and the volume of gas molecules.
- vapour pressure
-
The partial pressure exerted by evaporation of a liquid.
- wavelength
-
The distance between corresponding points in two adjacent light cycles.