Question

What is violation of the Pauli exclusion principle?

Answer 1

Violation of the Pauli exclusion principle:

• This is just a repetition of Pauli's exclusion principle, which states that no two electrons in an atom may have the same $4$ principal quantum number.
• No two electrons in an atom should have the same four electronic quantum numbers.
• The two electrons must have opposing spins, as an orbital can only hold two electrons at a time.
• This indicates that if one electron is allocated to spin up $(+1/2)$, the second electron must be assigned to spin down$(-1/2)$.
• For beryllium atoms, the $1\mathrm{s}$ and $2\mathrm{s}$ subshells can only carry two electrons, and when full, the electrons ought to have opposing spins.