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33 Cards in this Set

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An atom of the same element with different number of neutrons

Atomic number

The number of protons in the nucleus of an atom

Mass/Nucleon Number

The number of particles (protons and neutrons) in the nucleus of an atom.

Relative isotopic mass

The mass of an atom of an isotope compared with one-twelfth the mass of an atom of carbon-12.

Relative atomic mass

The weighted mean mass of an atom of an element compared with one-twelfth of the mass of an atom of carbon-12.

Relative molecular mass, (Mr)

The weighted mean mass of a molecule compared with one-twelfth of the mass of an atom of carbon-12.

Relative formula mass

The weighted mean mass of a formula unit compared with one-twelfth of the mass of an atom of carbon-12.

Amount of substance

The quantity whose unit is the mole, used as a means of counting atoms.

Avogadro constant, NA

The number of atoms per mole of the carbon-12 isotope (6.02x10^23 mol^-1).


Amount of any substance containing as many particles as there are carbon atoms in exactly 12g of the carbon-12 isotope. (6.02x10^23).

Molar mass, M

The mass per mole of a substance. The units of molar mass are g mol^-1 (grams per mole).

Empirical formula

The simplest whole-number ratio of atoms of each element present in a compound.


A small group of atoms held together by covalent bonds.

Molecular formula

The actual number of atoms of each element in a molecule.

Molar volume

The volume per mole of a gas. The units of molar volume are dm^3 mol^-1. At room temperature and pressure, the molar volume is approximately 24.0 dm^3 mol^-1.


Amount of solute, in mol, dissolved per 1dm^3 (1000cm^3) of solution.

Standard solution

A solution of known concentration. They are usually used in titrations to determine unknown information about another substance.


Any type of particle that takes part in a chemical reaction.


The molar relationship between relative quantities of substances taking part in a reaction (species).


A species that is a proton (H+ ion) donor.


A species that is a proton (H+ ion) acceptor.


A type of base that dissolves in water forming hydroxide ions, OH-(aq) ions.


Any chemical compound formed from an acid when a Proton (H+ ion) from the acid has been replaced by a metal ion or another positive ion, such as the ammonium ion, NH4^+


A crystalline compound containing water molecules.


A substance that contains no water molecules.

Water of crystallisation

Water molecules that form an essential part of the crystalline structure of a compound.

Oxidation number

A measure of the number of electrons that an atom uses to bond with atoms of another element.


The loss of electrons or an increase of oxidation number.


A gain of electrons or a decrease in oxidation number.

Redox reaction

A reaction in which both reduction and oxidation take place.

Reducing agent

A reducing agent is a reagent that reduces (adds electrons to) another species.

Oxidising agent

A reagent that oxidises (takes electrons from) another species).

Explain why ice is less dense than water, in terms of hydrogen bonding.

Ice is less dense than water as the hydrogen bonds in ice are longer and thus space the molecules out more. In water, the hydrogen bonds collapse, not as rigid and are closer together.