Orbital Diagrams and Electron Configurations

Question 1

Aufbau Principle

Answer 1

• the rule says that electrons are added to the lowest energy levels first
• why the 1s orbital is filled before the 2s orbital
• use the filling diagram

Question 2

Electron Spin

Answer 2

• spin: a property of electrons that may be thought of as clockwise (spin up) or counter-clockwise (spin down)
• a vertical arrow indicates and electron and its spin orientation

Question 3

Pauli-Exclusion Principle

Answer 3

-No more than 2 electrons may bein an atomic orbital and they must have opposite spin

Question 4

Energy and stability

Answer 4

• unstable electrons become more stable by losing energy
• electrons repel each other, so it is more stable to have only one electron in each orbital
• why certain exceptions exist

Question 5

Hund’s rule

Answer 5

• every orbital in a subshell needs to have 1 electron before another is added

Question 6

Copper (Cu)

Answer 6

Electron Configurations:
[Ar] 4s¹ 3d¹⁰
1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d¹⁰

Notice how one of the 4s electrons was moved to the 3d orbitals to complete the subshell and to make the element more stable

Question 7

Chronium (Cr)

Answer 7

Electron Configurations:
[Ar] 4s¹ 3d⁵
1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d⁵

Notice how one of the 4s electrons was moved to 3d, so that it could be filled halfway.