Definition list

Question 1

Atomic Number

Answer 1

the atomic number of an atom is the number of protons present in the nucleus of an atom,

Question 2

MASS NUMBER

Answer 2

The mass number is the number of protons plus neutrons in the nucleus of an atom.

Question 3

ISOTOPES

Answer 3

isotopes are atoms of the same element that have the same atomic number but different mass numbers
due to the different numbers of neutrons present in the nucleus.

Question 4

RELATIVE ATOMIC MASS

Answer 4

the average mass of an atom of an element compared to 1/12 the mass of the carbon –12 isotope, taking
relative abundances of isotopes into account.

Question 5

RELATIVE MOLECULAR MASS

Answer 5

the average mass of a molecule of a compound compared to 1/12 the mass of the carbon – 12 isotope,
taking relative abundances of isotopes into account.

Question 6

RADIOACTIVITY

Answer 6

is the spontaneous disintegration of the nucleus with the emission of α,β or γ radiation.

Question 7

NUCLEAR REACTION

Answer 7

a nuclear reaction involves a change in the nucleus of an atom and a new element is usually formed as a
result.

Question 8

CHEMICAL REACTION

Answer 8

– a chemical reaction involves electrons being shared or transferred from on atom to another – the nucleus
of the atom remains the same

Question 9

HALF-LIFE

Answer 9

this is the time taken for half the nuclei in a given sample to decay.

Question 10

HEISENBERG’S UNCERTAINTY PRINCIPLE

Answer 10

This states that it is impossible to know both the position and the speed of an electron at the same time as
electrons move in a wave motion

Question 11

ATOMIC ORBITAL

Answer 11

an atomic orbital is a region in space around the nucleus of an atom in which there is a high probability of
finding an electron

Question 12

ENERGY LEVEL

Answer 12

is the discrete amount of energy an electron has when it is in an atom

Question 13

TRANSITION ELEMENT

Answer 13

an element that forms at least one ion with a partially filled d- sublevel.

Question 14

D-BLOCK ELEMENT

Answer 14

an element whose highest energy electron occupies a d- sublevel.

Question 15

AUFBAU PRINCIPLE

Answer 15

electrons occupy the lowest available energy level

Question 16

HUNDS RULE OF MAXIMUM MULTIPLICITY

Answer 16

when two or more orbitals of equal energy are available (i.e. 2px 2py 2pz ), electrons fill them singly
before filling them in pairs

Question 17

PAULI EXCLUSION PRINCIPLE

Answer 17

no more than two electrons can occupy an orbital and this they can only do if they have opposite spin

Question 18

FIRST IONISATION ENERGY

Answer 18

this is the minimum amount of energy required to remove the first most loosely bound electron from a mole
of isolated atoms of an element in its neutral gaseous ground state.

Question 19

A MOLE

Answer 19

– a mole of a substance is that amount of it which contains the Avogadro’s constant number of particles

Question 20

AVOGADRO’S CONSTANT

Answer 20

– is the number of carbon atoms in exactly 12 grams of the C-12 isotope. This equals 6×10²³ particles.

Question 21

AVOGADRO’S LAW

Answer 21

equal volumes of all gases at the same temperature and pressure contain equal numbers of molecules.

Question 22

MOLAR MASS

Answer 22

the molar mass of a substance is its atomic mass (or its molecular mass) expressed in grams.

Question 23

MOLAR VOLUME

Answer 23

at s.t.p. the molar volume of any gas occupies a volume of 22.4litres (22,400cm3)

Question 24

LIMITING REACTANT

Answer 24

• the limiting reactant is the reactant that is fully consumed when a reaction goes to completion

Question 25

THEORETICAL YIELD

Answer 25

the theoretical yield of a reaction is the quantity of product that should form when all of the limiting reactant
reacts. To get the theoretical yield use the molar ratio from the balanced equation between the limiting reactant
and product.

Question 26

ACIDS- Arhenius’ theory

Answer 26

An acid produces H+ ions in water

Question 27

MONOBASIC ACID

Answer 27

A monobasic acid produces one H+ ion in solution e.g HCL & HNO3

Question 28

DIBASIC ACID

Answer 28

A dibasic acid produces two H+ ions in solution e.g H2SO4

Question 29

TRIBASIC ACID

Answer 29

A tribasic acid produces three H+ ions in solution e.g H3PO4

Question 30

BASES- Arhenius’ theory

Answer 30

A base produces OH- ions in water.

Question 31

ACID- Bronsted-Lowry threory

Answer 31

• an acid is a proton (H+ ) donor

Question 32

BASE- Bronsted-Lowry theory

Answer 32

a base is a proton (H+ ) acceptor.