### GCSE Physics

Energy
Forces
Forces and Motion
Waves in Matter
Electricity
Magnetism and Electromagnetism
Particle Model of Matter
Atomic Structure
Space Physics

# Nuclear Decay Equations

During radioactive decay, an unstable nucleus will emit alpha or beta particles. We can describe the changes by using nuclear equations. The format for a nuclear equation is:

Atom before decayatom after decay + radiation emitted

In nuclear decay equations, the sum of the mass and atomic numbers should be the same before and after the reaction.

• Gamma radiation is pure energy. It does not have any mass or charge, so it will not change the mass or charge of the nucleus.

## Alpha Decay

During alpha decay, the alpha particle is emitted from an unstable nucleus. Due to the +1 charge of each proton, the charge of the nucleus decreases by 2. Also, the atomic number decreases by 2 and the mass number decreases by 4.

• A completely different element is formed in the process

The diagram below shows uranium undergoing alpha decay.

When uranium-238 undergoes alpha decay, it forms thorium-234. The nuclear equation is:

$\mathrm{}_{92}^{238}U\to \mathrm{}_{90}^{234}Th+\mathrm{}_{2}^{4}\alpha$

## Beta Decay

Beta decay affects the overall charge of the nucleus. During this process, a neutron in the nucleus transforms into a proton, and an electron (beta particle) is emitted. Since the proton number increases by 1, the positive charge of the nucleus increases. However, the mass number does not change.

As the atomic number changes, a completely different element is formed.

Below is an example of an equation for beta decay:

• In nuclear equations, the beta particle is represented with an atomic number of -1 due to its negative charge.

A beta particle is a high-speed electron, so it has no mass. This means that the mass number does not change. Since a neutron changes into a proton during beta decay, the atomic number of the atom increases by 1.

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