Radioactivity

Question 1

Radioactive Decay

Answer 1

A nucleus with too many or too few neutrons means that it is unstable and will decay in a random process, emitting radiation as it does so.

Question 2

Types of Radioactive Decay

Answer 2

An unstable nucleus can decay by emitting an alpha particle, a beta minus particle, an beta positive (positron), or a gamma ray, or in some cases a single neutron.

Question 3

Alpha Particle

Answer 3

If a nucleus is unstably large, it will emit a ‘package’ of two protons and neutrons called an Alpha Particle.

It is also a helium 4 nucleus, so it is written as 4( the number on top) and 2 (number at the bottom) H or replace it with an A.

Alpha decay causes the mass number of the nucleus to decrease by 4 and the atomic number by two.

Question 4

Beta Minus Particle

Answer 4

If the nucleu has two many neutrons, neutron will turn into a proton and emit a fast-moving electron. This electron is known as the Beta Minus Particle.

Has a mass of 0 and has atomic number as -1.

Question 5

Positron Emission

Answer 5

If a nucleus has too few neturons, a proton will turn into a neutron and emit a fast-moving electron.

Mass of O but atomic number of +1.

Question 6

Gamma Ray

Answer 6

Gamma ray emissions cause no change in the number of particles in the nucleus meaning both the atomic number and mass stays the same.

Question 7

Properties of Nuclear Radiation

Answer 7

Alpha - can be stopped by skin or paper.

• most ionising(converting into a charged particle)
• least penetrable

Beta - can be stopped by aluminium foil

• Middle in ionising
• Middle in penetrating

Gamma - Can be stopped by thick lead or concrete

• Last in ionising
• Most penetrating

Question 8

Half-Life

Answer 8

The time it takes for half of the unstable nuclei in a sample to decay.