Question

1. draw orbital diagrams for the following elements: oxygen: how many unpaired electrons are there? magnesium: how many unpaired electrons are there?

Explanation:

Step1: Determine electron - configuration of oxygen

Oxygen has atomic number 8. Its electron - configuration is $1s^{2}2s^{2}2p^{4}$.

Step2: Draw orbital diagram for oxygen

The 1s orbital has 2 paired electrons (↑↓), the 2s orbital has 2 paired electrons (↑↓), and the 2p orbitals (three 2p orbitals) have 4 electrons. According to Hund's rule, the first 3 electrons in the 2p orbitals are unpaired (↑ ↑ ↑) and the fourth pairs up with one of them (↑↓ ↑ ↑). So, oxygen has 2 unpaired electrons.

Step3: Determine electron - configuration of magnesium

Magnesium has atomic number 12. Its electron - configuration is $1s^{2}2s^{2}2p^{6}3s^{2}$.

Step4: Draw orbital diagram for magnesium

The 1s orbital has 2 paired electrons (↑↓), the 2s orbital has 2 paired electrons (↑↓), the 2p orbitals have 6 paired electrons (↑↓ ↑↓ ↑↓), and the 3s orbital has 2 paired electrons (↑↓). So, magnesium has 0 unpaired electrons.

Answer:

Oxygen: Orbital diagram: 1s(↑↓) 2s(↑↓) 2p(↑↓ ↑ ↑), 2 unpaired electrons.
Magnesium: Orbital diagram: 1s(↑↓) 2s(↑↓) 2p(↑↓ ↑↓ ↑↓) 3s(↑↓), 0 unpaired electrons.