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 periodicity?

Answer 7

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

Question 8

What is first ionisation energy?

Answer 8

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

Question 9

What is metallic bonding?

Answer 9

• The strong electrostatic attraction between cations and delocalised electrons

Question 10

What are giant covalent lattices?

Answer 10

• Networks of atoms bonded by strong covalent bonds

Question 11

What is disproportionation?

Answer 11

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

Question 12

What is the standard enthalpy change of formation, and its symbol?

Answer 12

• The enthalpy change that takes place when one mole of a compound is formed from its elements under standard conditions, with all reactants and products in their standard states
• ΔfH⦵

Question 13

What is the standard enthalpy change of combustion, and its symbol?

Answer 13

• The enthalpy change that takes place when one mole of a substance is reacted completely with oxygen under standard conditions, with all reactants and products in their standard states
• ΔcH⦵

Question 14

What is the standard enthalpy change of neutralisation, and its symbol?

Answer 14

• The enthalpy change that accompanies the reaction of an acid by a base to form one mole of H2O (l) under standard conditions, with all reactants and products in their standard states
• ΔneutH⦵

Question 15

What is average bond enthalpy?

Answer 15

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

Question 16

What is a buffer solution?

Answer 16

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

Question 17

What is lattice enthalpy, and its symbol?

Answer 17

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

Question 18

What is the definition of the standard enthalpy change of solution and its symbol?

Answer 18

• The enthalpy change that takes place when 1 mole of a solute dissolves in a solvent
• ΔsolH⦵

Question 19

What is the definition of the standard enthalpy change of hydration and its symbol?

Answer 19

• The enthalpy change that takes place when 1 mole of gaseous ions forms hydrated ions
• ΔhydH⦵

Question 20

What is entropy? Include its symbol and units.

Answer 20

• A measure of the dispersal of energy in a system, that is greater the more disordered a system is
• S and J K^-1 mol^-1