definitions

Question 1

isotope

Answer 1

atoms of the same element with the same number of protons but different number of neutrons

Question 2

relative atomic mass

Answer 2

the weighted mean mass
of an atom of an element
compared to the mass of 1/12th of an atom of carbon-12

Question 3

relative isotopic mass

Answer 3

the weighted mean mass
of an atom of an isotope
compared to the mass of 1/12th of an atom of carbon-12

Question 4

atomic orbital

Answer 4

a region within an atom that holds up to 2 electrons with opposite spins

Question 5

ionic bonding

Answer 5

electrostatic attraction between oppositely charged ions

Question 6

metallic bonding

Answer 6

electrostatic attraction between positive metal ions and a sea of delocalised electrons

Question 7

covalent bonding

Answer 7

electrostatic attraction between positive nuclei and shared pair of electrons

Question 8

dative bond

Answer 8

a type of covalent bond in which both of the electrons
in the shared pair come from one atom.

Question 9

mass spectometry

Answer 9

an instrument which gives accurate information about relative isotopic
mass and the relative abundance of isotopes.

Question 10

amount of substance

Answer 10

the number of particles in the substance, measured in moles

Question 11

mole

Answer 11

a unit containing exactly 6.02x10’23 elementary entities

Question 12

molar mass

Answer 12

mass per mole of a substance (units: g mol-1)

Question 13

waters of crystallisation

Answer 13

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

Question 14

hydrated

Answer 14

a crystalline compound that contains water

Question 15

anhydrous

Answer 15

a crystalline compound that contains no water

Question 16

empirical formula

Answer 16

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

Question 17

acid

Answer 17

compounds that release H+ ions in aqueous solution.

Question 18

alkali

Answer 18

water soluble bases. Alkalis release OH- ions into aqueous solution

Question 19

base

Answer 19

a substance that can accept H+ ions from another substance.

Question 20

strong acid

Answer 20

an acid that completely dissociates in solution

Question 21

weak acid

Answer 21

an acid that partially disassociates in solution

Question 22

oxidation

Answer 22

loss of electrons

Question 23

reduction

Answer 23

gain of electrons

Question 24

oxidation number

Answer 24

a number that represents the number of electrons lost/gained by an
atom of an element

Question 25

energy level

Answer 25

the shell that an electron is in

Question 26

subshell

Answer 26

a subdivision of the electronic shells into different orbitals

Question 27

average bond enthalpy

Answer 27

the average energy required to break a bond, used as a
measurement of the strength of a covalent bond

Question 28

bonding pair

Answer 28

a pair of outer-shell electrons involved in bonding

Question 29

electronegativity

Answer 29

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

Question 30

lone pair

Answer 30

a pair of outer-shell electrons not involved in bonding

Question 31

enthalpy change

Answer 31

the change in heat energy of a substance at constant pressure

Question 32

hess’ law

Answer 32

the enthalpy change for a chemical reaction is independent of the route taken
sum of clockwise enthalpy= sum of
anti-clockwise enthalpy

Question 33

standard conditions

Answer 33

100kPa
298k

Question 34

standard enthalpy change of formation

Answer 34

• when one mole of product is formed
• from it’s products
• under standard conditions

Question 35

standard enthalpy change of combustion

Answer 35

-when one mole of substance
- burns completely in excess oxygen
- under standard conditions

Question 36

standard enthalpy change of neutralisation

Answer 36

• when one mole of water is formed
• from a neutralisation reaction
• under standard conditions

Question 37

ionisation

Answer 37

removal of an electron form an atom to form a positive ion

Question 38

first ionisation energy

Answer 38

the energy needed to remove one electron from each atom
in a mole of gaseous atoms
to make one mole of gaseous unipositive ions.

Question 39

second ionisation energy

Answer 39

the energy needed to remove one electron from each atom
in a mole of gaseous unipositive ions
to make one mole of gaseous dipositive ions

Question 40

successive ionisation energy

Answer 40

amount of energy needed to remove the first, second, and subsequent electrons from one mole of gaseous atoms

Question 41

ionic lattice

Answer 41

a repeating pattern of oppositely charged ions