7.3 Changes in the nucleus

Question 1

Atomic number def

Answer 1

The number of protons (which equals the number of electrons) in an atom

Question 2

Mass number def

Answer 2

The number of protons and neutrons in a nucleus

Question 3

Isotope def

Answer 3

Atoms with the same number of protons and different numbers of neutrons

Question 4

What is an alpha particle made up of, what is its relative charge and what is its atomic mass

Answer 4

• it is made up of two protons and two neutrons
• its relative mass is 4
• its relative charge is +2

Question 5

How can you also represent an alpha particle

Answer 5

as a helium nucleus

Question 6

what happens (to atomic number and mass) when an unstable nucleus emits an alpha particle

Answer 6

• atomic number goes down by 2
• mass number goes down by 4
• the mass and charge of the nucleus are reduced

Question 7

when is a beta particle emitted

Answer 7

by a nucleus that has too many neutrons compared with its protons

Question 8

what happens in beta radiation

Answer 8

a neutron in the nucleus changes into a proton and a beta particle (i.e. an electron)

Question 9

what is the relative charge and mass of a beta particle

Answer 9

• mass is 0
• charge is -1

Question 10

what happens when an unstable nucleus emits a beta particle

Answer 10

• atomic mass stays the same
• atomic number goes up by 1 (neutron changes into a proton)
• charge of the nucleus is increased and mass stays the same

Question 11

what happens when the nucleus emits a gamma ray

Answer 11

nothing because the gamma ray is uncharged and it has no mass

Question 12

why are neutrons emitted by some radioactive substances

Answer 12

• as a result of alpha particles colliding with unstable nuclei in the substance
• this collision causes a nucleus to become even more unstable and emit a neutron
• because neutrons are uncharged, they can pass through substances more easily than alpha or beta particles