How is the mass number calculated for an atom involved in nuclear fusion?

if two electrons have the same n, the same ℓ, and the same ml, then they are in the same orbital. the pauli exclusion principle states that no two identical fermions (a fancy word for electrons and other subatomic particles like electrons) may occupy the same quantum state in an atom simultaneously.

it forms an anion that has a larger radius. anions have a negative charge and are larger than the original atom.