When a Lithium Atom Is Made from a Helium Atom

Multiple Choice

When a lithium atom is made from a helium atom by adding a proton (and neutron) to the nucleus and an electron outside, the electron goes into an n = 2, ℓ=0 state rather than an n = 1, ℓ=0 state.This is an indication that electrons:

A) obey the Pauli exclusion principle
B) obey the minimum energy principle
C) undergo the Zeeman effect
D) are diffracted
E) and protons are interchangeable