Electron Configuration

Question 1

Aufbau’s Principle

Answer 1

each new electron occupies the lowest energy orbital. e.g. 1s has lower energy than 2p so electrons fill 1s first.

Question 2

Hund’s Rule

Answer 2

single electrons with the same spin must occupy each equal energy orbital before adding additional electrons with opposite spins.

Question 3

Pauli’s Exclusion Principle

Answer 3

a maximum of two electrons may occupy a single electron but only if the electrons have opposite spins.

Question 4

Chromium and Copper Exception

Answer 4

both 4s becomes 1 and the 3d becomes 3d5 for chromium and 3d10