Types of radiation – WJECNuclear equations

Nuclear equations show single alpha and beta decay.

Symbols

The nucleus of an atom can be represented as

A is the atomic mass (number of protons + neutrons)

Z is the atomic number (number of protons)

X is the chemical symbol (as shown in the periodic table)

Alpha decay

Two protons and two neutrons are lost from a nucleus when it emits an alpha particle. This means that:

• the atomic mass number decreases by 4
• the atomic number decreases by 2

A new element is formed that is two places to the left in the periodic table than the original element.

For example, radon decays into polonium when it emits an alpha particle. Here is the equation for that radioactive decay.

Beta decay

In beta decay, a neutron changes into a proton plus an electron. The proton stays in the nucleus. The electron leaves the atom with high energy as a beta particle.

The nucleus has one more proton and one less neutron when it emits a beta particle. This means that:

• the atomic mass number stays the same
• the atomic number increases by 1

For example, carbon-14 is a radioactive isotope of carbon. Here is the equation for the beta decay of carbon-14 into nitrogen.