Chemical Equation and Atomic Numbers

What is the atomic number of the unknown atom X in the nuclear equation below?

Consider the nuclear equation below:

239Pu --> X + 4He

94 2

Answer:

The atomic number of the unknown atom X in the nuclear equation is 92.

In balancing chemical equations, the mass number and atomic number must be conserved. This implies that the sum of atomic numbers (subscript) on the left-hand side must be equal to that on the right-hand side. Also, the sum of the mass numbers (superscript) on the left-hand side must be equal to that on the right-hand side.

For the mass numbers:

239 = a + 4

a = 239 - 4 = 235

For atomic numbers:

94 = n + 2

n = 94 - 2 = 92

Therefore, the atom X has a mass number of 235 and an atomic number of 92. This can be written as 23592X. So, the atomic number of the unknown atom X is 92.