key AS definitions

Question 1

isotopes

Answer 1

atoms of the same element with the same atomic number (number of protons) but a different mass number (number of neutrons)

Question 2

orbital

Answer 2

a volume of space around the nucleus that can hold up to 2 electrons with opposite spin

Question 3

ionic bond

Answer 3

electrostatic attraction between positive and negative ions

Question 4

covalent bond

Answer 4

strong electrostatic attraction between shared pair of electrons and the nuclei of the bonded atoms

Question 5

dative covalent bond

Answer 5

a shared pair of electrons where one atom contributes both electrons to the shared pair

Question 6

average bond enthalpy

Answer 6

energy required to break 1 mol of bonds in gaseous state

Question 7

electronegativity

Answer 7

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

Question 8

ionisation energy

Answer 8

energy required to remove 1mol of electrons from 1 mol of gaseous atoms to produce 1mol of 1+ gaseous ions

Question 9

oxidation

Answer 9

loss of electrons/oxidation number increases

Question 10

reduction

Answer 10

gain of electrons/decrease of oxidation number

Question 11

disproportionation

Answer 11

same element is reduced and oxidised

Question 12

relative atomic mass

Answer 12

weighted mean mass of an atom of an element compared with one 12th of the mass of a carbon 12 atom

Question 13

relative isotopic mass

Answer 13

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

Question 14

dynamic equilibrium

Answer 14

closed system; rate of forward = rate of backward; conc of reactants and products does not change

Question 15

empirical formula

Answer 15

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

Question 16

molecular formula

Answer 16

actual number of atoms of each element present in a molecule

Question 17

general formula

Answer 17

simplest algebraic formula for a member of a homologous series

Question 18

structural formula

Answer 18

shows arrangement of atoms in a molecule

Question 19

displayed formula

Answer 19

shows how atoms are arranged and shows all bonds between them

Question 20

skeletal formula

Answer 20

shows bonds of carbon skeleton only

Question 21

radical

Answer 21

a species with an unpaired electron

Question 22

homolytic fission

Answer 22

breaking of a covalent bond, with one of the bonding electrons going to each atoms forming two radicals

Question 23

heterolytic fission

Answer 23

breaking of a covalent bond with both electrons going to one atom, forming an anion and a cation

Question 24

substitution reaction

Answer 24

a reaction in which one atom or group of atoms is replaced by another atom or group of atoms

Question 25

electrophile

Answer 25

an electron pair acceptor eg. Br+

Question 26

nucleophile

Answer 26

has a lone pair of electrons; attracted to a +carbon, donates a lone pair of electrons

Question 27

homologous series

Answer 27

a series of organic compounds with the same functional group but with each successive member of the group differing by CH2

Question 28

functional group

Answer 28

a group of atoms responsible for the characteristic reactions of a compound

Question 29

aliphatic

Answer 29

carbons joined in straight chains, branched chains or non-aromatic rings

Question 30

alicyclic

Answer 30

carbons joined in rings but non aromatic rings

Question 31

aromatic

Answer 31

contains a benzene ring

Question 32

saturated

Answer 32

contains only single carbon-carbon bonds

Question 33

unsaturated

Answer 33

contains multiple carbon-carbon bonds