Definitions

Question 1

What are isotopes?

Answer 1

• Atoms of the same element which therefore have the same number of protons and electrons but a different number of neutrons

Question 2

What is relative isotopic mass?

Answer 2

• The mass of an isotope relative to 1/12th of the mass of an atom of carbon-12

Question 3

What is relative atomic mass?

Answer 3

• The weighted mean mass of an atom of an element relative to 1/12th of the mass of an atom of carbon-12

Question 4

What is ionic bonding?

Answer 4

• The electrostatic attraction between positive and negative ions

Question 5

What is an ionic lattice?

Answer 5

• A repeating pattern of oppositely charged ions

Question 6

What is a covalent bond?

Answer 6

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

Question 7

What is electronegativity?

Answer 7

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

Question 8

What is a hydrogen bond?

Answer 8

• A special type of permanent dipole-dipole interaction found between molecules containing:
• an electronegative atom (such as F, O and N) with a lone pair of electrons
• a hydrogen atom bonded to an electronegative atom

Question 9

What is periodicity?

Answer 9

• Repeating trends in the physical and chemical properties of elements across a period

Question 10

What is first ionisation energy?

Answer 10

• The energy required for the removal of 1 mol of electrons from 1 mol of gaseous atoms of an element

Question 11

What is metallic bonding?

Answer 11

• The strong electrostatic attraction between cations and delocalised electrons

Question 12

What are giant covalent lattices?

Answer 12

• Networks of atoms bonded by strong covalent bonds

Question 13

What is disproportionation?

Answer 13

• A redox reaction in which the same element is both oxidised and reduced simultaneously

Question 14

What is the standard enthalpy change of formation?

Answer 14

• The enthalpy change that takes place when one mole of a compound is formed from its elements under standard conditions

Question 15

What is the standard enthalpy change of combustion?

Answer 15

• The enthalpy change that takes place when one mole of a substance is reacted completely with oxygen under standard conditions

Question 16

What is the standard enthalpy change of neutralisation?

Answer 16

• The enthalpy change that accompanies the reaction of an acid by a base to form one mole of H2O (l) under standard conditions

Question 17

What is average bond enthalpy?

Answer 17

• When 1 mole of bonds of gaseous covalent bonds is broken

Question 18

What is a buffer solution?

Answer 18

• A system that minimises pH changes on addition of small amounts of an acid or a base

Question 19

What is lattice enthalpy?

Answer 19

• The enthalpy change when 1 mole of ionic lattice is formed from its gaseous ions

Question 20

What is the definition of the standard enthalpy change of solution?

Answer 20

• The enthalpy change that takes place when 1 mole of a solute dissolves in water

Question 21

What is the definition of the standard enthalpy change of hydration?

Answer 21

• The enthalpy change that takes place when 1 mole of gaseous ions form hydrated ions

Question 22

What is entropy?

Answer 22

• A measure of the dispersal of energy in a system, that is greater the more disordered a system is

Question 23

What is standard electrode potential?

Answer 23

• The e.m.f of a half-cell compared to a hydrogen half-cell

Question 24

What are the transition elements?

Answer 24

• Elements that form at least one ion with a partially filled d-orbital (not scandium and zinc)

Question 25

What is a ligand?

Answer 25

- A species with a lone pair of electrons that it donates to a central metal ion to form a dative covalent/ coordinate bond