Nuclear Equations

nuclear equation:  a chemical equation describing an isotope that is undergoing radioactive decay.  For example:

is a nuclear equation.

In a nuclear equation, the number of protons (atomic number) and the total mass (mass number) are both conserved on both sides of the arrow.  If you look at the bottom (atomic) numbers, and replace the arrow with an = sign, you would have the following:

92 = 90 + 2

Similarly, if you look at the top (mass) numbers, and replace the arrow with an = sign, you would have:

238 = 234 + 4

Sample problems:

What are the products of beta (β−) decay of ¹³¹I?

Answer:

A β− particle is an electron, which we write as  in a nuclear equation.  This means ¹³¹I decays into some unknown particle + .  The equation is:

We can write the following equations for the atomic and mass numbers:

Atomic #s:     53 = p + −1  à  p = 54; X = Xe

Mass #s:        131 = m + 0  à  m = 131

Therefore, particle X  is .  So our final answer is:

The two products of decay in this reaction are  and .
Which particle was produced in the following radioactive decay reaction:

Answer:

The two equations are:

Atomic #s:     86 = 84 + p  à  p = 2

Mass #s:        212 = 208 + m  à  m = 4

Therefore, particle X  has 2 protons and a mass of 4 amu, which means it is an α particle: .