Key Definitions

Question 1

Element

Answer 1

A substance that cannot be broken down into simpler substances by chemical means.
(Robert Boyle)

Question 2

Element

Answer 2

A substance whose atoms all have the same atomic number.

Question 3

Law of Conservation of Mass

Answer 3

States that matter cannot be created or destroyed in the course of a chemical reaction.

Question 4

Atomic Number

Answer 4

The number of PROTONS in the nucleus of an atom.

Question 5

Mass Number

Answer 5

The sum of the number of protons AND neutrons in the nucleus of an atom.

Question 6

Isotopes

Answer 6

Atoms with the same number of protons but different numbers of neutrons.

Question 7

Relative Atomic Mass

Answer 7

The average mass of an atom relative to 1/12 of the mass of an atom of Carbon-12

Question 8

Radioactivity

Answer 8

The spontaneous breaking up of unstable nuclei, accompanied by the emission of radiation.

Question 9

Alpha Particles

Answer 9

Have 2 protons + 2 neutrons (helium nuclei)
Have a POSITIVE charge and little penetrating ability.
Americium-241

Question 10

Beta Particles

Answer 10

Neutrons disintegrate into protons and electrons. The electrons are emitted in a fast-moving stream - negative charge.
Carbon-14

Question 11

Gamma Rays

Answer 11

Emitted by radioactive isotopes. No mass or charge, move very quickly.
High-energy electromagnetic radiation.
Cobalt-60

Question 12

Half-Life

Answer 12

The half-life of a radioactive isotope is the time taken for half of the atoms in the isotope to decay.

Question 13

Energy Level

Answer 13

A region of definite energy within the atom that electrons can occupy.

Question 14

Line Spectrum

Answer 14

A seriös of coloured lines against a dark background .

Question 15

Absorption Spectrum

Answer 15

The spectrum that is observed after white light had been passed through the element.

Question 16

Heisenberg Uncertainty Principle

Answer 16

States that is it not possible to determine the position and velocity of an electron at the same time.

Question 17

Atomic Orbital

Answer 17

A region in space where the probability of finding an electron is relatively high.

Question 18

Energy Sublevel

Answer 18

A group of atomic orbitals that all have the same energy.

Question 19

Aufbau Principle

Answer 19

States that electrons will occupy the lowest energy sublevel available.

Question 20

Atomic Radius

Answer 20

Half the distance between the nuclei of two atoms that are joined together by a single covalent bond.

Question 21

First Ionisation Energy

Answer 21

The minimum energy in kJ required to remove the most loosely bound electron from each isolated atom of the element in its ground state.

Question 22

Second Ionisation Energy

Answer 22

The energy required to remove the most loosely bound electron from each singly charged positive ion in a mole of these ions.

Question 23

Oxidation

Answer 23

The loss of electrons.
(Occurs at anode)

Question 24

Reduction

Answer 24

The gain of electrons.
(Occurs at cathode)

Question 25

Oxidising Agent

Answer 25

A substance that allows oxidation to happen by gaining electrons itself.

Question 26

Reducing Agent

Answer 26

A substance that allows reduction to happen by losing electrons itself.

Question 27

Electrolysis

Answer 27

The use of electric current to cause a chemical reaction.

Question 28

Electroplating

Answer 28

The costing of a metal onto the surface of another metal using electrolysis