Glossary (Definitions)

Question 1

Define mass number

Answer 1

protons + neutrons

Question 2

Define atomic number

Answer 2

protons or electrons

Question 3

Define isotope(s) (of an element)

Answer 3

atoms with the same number of protons and electrons but a different number of neutrons

Question 4

Define relative atomic mass

Answer 4

the average mass of an atom on a scale where an atom of carbon-12 is 12

Question 5

Define relative molecular mass

Answer 5

the average mass of a molecule on a scale where when an atom of carbon-12 is 12

Question 6

Define first ionisation energy

Answer 6

the energy needed to remove 1 electron from 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions

Question 7

Define second ionisation energy

Answer 7

the energy needed to remove 1 electron from 1 mole of gaseous 1+ ions to form 1 mole of gaseous 2+ ions

Question 8

Define Avogadro’s constant

Answer 8

number of particles in a mole (6.02 x 10^23 particles)

Question 9

Define empirical formula

Answer 9

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

Question 10

Define molecular formula

Answer 10

the actual number of atoms of each element in a compound

Question 11

Define compound

Answer 11

made up of two or more elements chemically bonded

Question 12

Define ionic bond

Answer 12

electrostatic attraction between oppositely charged metal and non-metal ions

Question 13

Define covalent bond

Answer 13

shared pairs of electrons between two non-metal atoms

Question 14

Define dative covalent bond

Answer 14

a covalent bond where the pair of electrons come from the same species

Question 15

Define lone pair

Answer 15

pair of electrons that are not bonded to anything

Question 16

Define electronegativity

Answer 16

an atom’s ability to attract the electron pair in a covalent bond

Question 17

Define dipole

Answer 17

a difference in charge between the two atoms caused by a shift in electron density in the bond

Question 18

Define metallic bond

Answer 18

electrostatic attraction between positive metal ions and delocalised electrons

Question 19

Define enthalpy change

Answer 19

the heat energy transferred in a reaction at constant pressure

Question 20

Define exothermic reaction

Answer 20

a reaction where energy is lost and exerted to the surroundings

Question 21

Define endothermic reaction

Answer 21

a reaction where energy is absorbed from the surroundings

Question 22

Define mean bond enthalpy

Answer 22

the average energy needed to break a certain type of bond

Question 23

Define standard enthalpy of formation

Answer 23

the enthalpy change when 1 mole of a compound is formed from its elements in their standard states under standard conditions

Question 24

Define standard enthalpy of combustion

Answer 24

the enthalpy change when 1 mole of a substance is completely burned in oxygen under standard conditions

Question 25

Define Hess’s law

Answer 25

the total enthalpy change of a reaction is independent of the route taken