Ocr Chemistry As Level Definitions

Front 1

Isotope

Back 1

Atoms of the same element with different numbers of neutrons and masses

Front 2

Relative isotopic mass

Back 2

Mass of an isotope of an element compared to the mass of 1/12 of an atom of C-12

Front 3

Relative atomic mass

Back 3

Weighted mean mass of an element compared to 1/12 of the mass of an atom of C-12

Front 4

Empirical formula

Back 4

The simplest whole number ratio of atoms of elements in a compound

Front 5

Molecular formula

Back 5

The number and type of atoms of each element in a compound

Front 6

Acid

Back 6

Proton donor

Releases H+ ions when added to water

Front 7

Base/alkali

Back 7

Base accepts protons

Alkalis release OH- ions when addes to water

Front 8

Ionic bonding

Back 8

Strong electrostatic force of attraction between two oppositely charged ions

Front 9

Covalent bond

Back 9

Strong electrostatic force of attraction between a shared pair of electrons and the nuclei of the bonded atoms

Front 10

Average bond enthalpy

Back 10

A measurement of the energy needed to break one mole of bonds in a gaseous state averaged for all conpounds bond is present in

Front 11

Electronegativity

Back 11

The ability of an atom to attract the bonding electrons in a covalent bond

Front 12

First ionisation energy

Back 12

The energy needed to remove one mole of electrons from one mole of gaseous atoms

Front 13

Metallic bonding

Back 13

The strong electrostatic force between cations and delocalised electrons

Front 14

Enthalpy change of reaction

Back 14

Enthalpy change when reaction occurs in molar quantities stated in balanced chemical equation

Front 15

Enthalpy change of formation

Back 15

Enthalpy change when 1 mole of a compound is formed from its elements

Front 16

Enthalpy change of combustion

Back 16

Enthalpy change when one mole of a compiund is completley burnt in oxygen

Front 17

Enthalpy change of neutralisation

Back 17

Enthalpy change when 1 mole of water is formes from reaction of acid and base

Front 18

General formula

Back 18

Simplest algebraic formula of a homologous series

Front 19

Homologous series

Back 19

Series of organic compoumds with same general formula and functional groups

Front 20

Functional group

Back 20

Group of atoms responsibke for the characteristic reactions of a compound

Front 21

Aliphatic compound

Back 21

Compiund not containing benzene ring

Front 22

Alicyclic

Back 22

Arranged in non-aromatic rings

Front 23

Aromatic

Back 23

Contains benzene ring

Front 24

Structural isomer

Back 24

Same molecular formula but differeny structural formula

Front 25

Radical

Back 25

A species with an unpaired electron

Front 26

Stereoisomers

Back 26

Same structural formula but different arrangement in space