Nuclear reaction balance

In every nuclear reaction two quantities are conserved: the sum of mass numbers $A$ (the superscript) and the sum of atomic numbers $Z$ (the subscript) on both sides of the equation:

$\sum A_{\text{reactants}}=\sum A_{\text{products}},\qquad \sum Z_{\text{reactants}}=\sum Z_{\text{products}}$

So by marking one species as the unknown "?", you can work out its $A$ and $Z$ and then identify the element (from $Z$ in the periodic table) or the particle:

• α particle: $A=4,\ Z=2$ (the ⁴₂He nucleus),
• β⁻ particle: $A=0,\ Z=-1$ (electron), β⁺: $A=0,\ Z=+1$,
• neutron: $A=1,\ Z=0$, proton: $A=1,\ Z=1$, γ: $A=0,\ Z=0$.

The calculator also checks whether the reaction you enter is correctly balanced.