Nuclear Decay Equations

This lesson covers:

  1. How alpha and beta particles can be written as 24He24He and −1   0e{-1}{\ \ \ 0}e 
  2. The nuclear equations for alpha, beta, gamma, and neutron decay

When writing nuclear decay equations, we only care about the nuclei of atoms. So when we write something like:

24​He

We're describing a helium atom's nucleus:

  1. The He is the elemental symbol (also called the chemical symbol) for helium.
  2. The 4 is the mass number. This is the total number of protons and neutrons that the nucleus contains.
  3. The 2 is the atomic number. This is the number of protons.

However, you can also think of the atomic number as the particle's charge.

So the helium nucleus above has a positive charge of 2 (+2).

For comparison, if you see something like this:

0−1​β
  1. The β represents a 'beta particle'.
  2. The 0 means that the particle contains zero protons or neutrons.
  3. The -1 means that the particle has a negative 1 (-1) charge, which is because it contains 1 negative electron.

Which two the following represent an alpha particle?

24He24He

−1   0β{-1}{\ \ \ 0}\beta   

γ\gamma

24α24\alpha

0

/

2

Nuclear equation showing thorium undergoing alpha decay with missing atomic mass and atomic number.

The above nuclear equation shows thorium (Th) undergoing alpha decay.


Fill in the missing atomic mass (A)and atomic number (B):


A:

B:

228
88

0

/

2

Which of the following represent a beta particle?

−1   0e{-1}{\ \ \ 0}e

−1   0β{-1}{\ \ \ 0}\beta   

24He24He

γ\gamma

0

/

2

Nuclear equation showing rubidium undergoing beta decay with missing atomic mass A and atomic number B.

The above nuclear equation shows rubidium (Rb) undergoing beta decay.


Fill in the missing atomic mass A and atomic number B:


A:

B:

87
38

0

/

2

Which of the following represents gamma radiation?

24α24\alpha

γ\gamma

−1   0β{-1}{\ \ \ 0}\beta   

24He24He

0

/

1

Nuclear equation showing protactinium undergoing gamma ray decay with missing atomic mass A and atomic number B.

The above nuclear equation shows protactinium (Pa) undergoing gamma ray decay.


Fill in the missing atomic mass A and atomic number B:


A:

B:

234
91

0

/

2

Which of the following represents a neutron?

10n10n

01n01n

11n11n

0

/

1

Nuclear equation showing xenon undergoing neutron decay with missing atomic mass number A and atomic number B.

The above nuclear equation shows xenon (Xe) undergoing neutron decay.


Fill in the missing atomic mass number (A) and atomic number (B):


A:

B:

137
54

0

/

2

element / molecule / protons / neutrons


The nucleus of any can be represented in the following form:


  612C{\ \ 6}{12}C


This is the nucleus of the element carbon.


  1. The C is the elemental (or chemical) symbol
  2. The 12 is the 'mass number', which is the number of protons and neutrons combined
  3. The 6 is the 'atomic number', which is the number of . This can also be thought of as the particle's charge.
element
protons

0

/

2