Aufbau Principle

Chemistry

Hund´s rule.

The most stable arrangement of electrons in a given sub shell is the one with the most unpaired electron.

Pauli rule.

Only two electrons permitted per orbital and they must have opposite spins as no two electrons may have the most unpaired electrons.

Aufbau principle.

This principle states that electrons  fill lower-energy atomic orbitals before filling higher-energy ones.

Practice questions.

Multiple Choice

One of the following does not represent the ground state electron configuration for an atom. Which one?

• [NE] 3s1 , 3p5

• [NE] 3s1, 3p3

• [NE] 3s1

• [NE] 3s2