DEFINITIONS

Question 1

Relative isotopic mass

Answer 1

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

Question 2

Relative atomic mass, Ar

Answer 2

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

Question 3

Relative molecular mass, Mr

Answer 3

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

Question 4

Relative formula mass, Mr

Answer 4

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

Question 5

1st ionisation energy

Answer 5

the energy required to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions

Question 6

degenerate (when applied to orbitals)

Answer 6

of identical energy

Question 7

amount of substance

Answer 7

the quantity whose unit is the mole. Used as a means of counting atoms.

Question 8

the mole

Answer 8

the amount of any substance containing as many particles as there are carbon atoms in exactly 12g of the carbon-12 isotope

Question 9

Avogadro constant

Answer 9

the number of atoms per mole of the carbon-12 isotope (6.02x1023 mol-1)

Question 10

molar mass

Answer 10

the mass per mole of a substance in gmol-1

Question 11

empirical formula

Answer 11

the simplest whole number ratio of atoms of each element present in a compound

Question 12

molecular formula

Answer 12

the actual number of atoms of eachh element in a molecule

Question 13

anhydrous

Answer 13

substance containing no water molecules

Question 14

hydrated

Answer 14

crystalline compound containing water molecules

Question 15

water of crystallisation

Answer 15

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

Question 16

Oxidation number

Answer 16

A measure of the number of electrons that an atom uses to bond with atoms of another element. Derived from a set of rules

Question 17

Reducing agent

Answer 17

A reagent that reduces another species

Question 18

Oxidising agent

Answer 18

A reagent that oxidises another species

Question 19

Ionic bond

Answer 19

The electrostatic attraction between the oppositely charged ions

Question 20

Giant ionic lattice

Answer 20

Three dimensional structure of opposite,y charged ions held together by strong ionic bonds

Question 21

Covalent bonds

Answer 21

Bond formed by a shared pair of electrons

Question 22

Lone pair

Answer 22

An outer shell pair of electrons that is not involved in chemical bonding

Question 23

Dative covalent/coordinate bond

Answer 23

Shared pair of electrons provided by one of the bonding atoms only

Question 24

Electronegativity

Answer 24

Measure of the attraction of a bonded atom for the pair of electrons in a covalent bond

Question 25

Permanent dipole

Answer 25

A small charge difference across a bond that results from a difference in the electronegativities of the bonded atoms

Question 26

polar molecule

Answer 26

has an overall dipole when you take into account any dipoles across the bonds

Question 27

intermolecular force

Answer 27

an attractive force between neighbouring molecules

Question 28

permanent dipole-dipole force

Answer 28

a weak attractive force between permanent dipoles in neighbouring polar molecules

Question 29

van der Waals’ forces

Answer 29

attractive forces between induced dipoles in neighbouring molecules

Question 30

a hydrogen bond

Answer 30

a strong dipole-dipole attraction between:

• an electron-deficit hydrogen atom on one molecule; and
• a lone pair of electrons on a highly electronegative atom on a different molecule

Question 31

metallic bonding

Answer 31

the electrostatic attraction between positive metal ions and delocalised electrons

Question 32

giant metallic lattice

Answer 32

3d structure of positive ions and delocalised electrons, bonded together by strong metallic bonds

Question 33

simple molecular lattic

Answer 33

3-d structure of molecules, bonded together by weak intermolecular forces

Question 34

giant covalent lattice

Answer 34

3-d structure of atoms, bonded together by strong covalent bonds