Explain anomalous behavior of Oxygen.

Oxygen is the first Element of group 16. 

Reasons for anomalous behavior of Oxygen: 

• Small size 
• Electronegativity 
• No d-orbitals in valence shell 

Oxygen shows following anomalous Behaviour:

1. Atomicity: Oxygen exists as a diatomic molecule while other elements of group 16 are polyatomic Molecules and they have puckered ring structure. 

2. Magnetic behavior: Molecular oxygen O2 is paramagnetic in nature while other elements of group 16 are diamagnetic. Because Molecular O2 has unpaired Electrons in the antibonding molecular orbital. 

3. Oxidation states: Oxygen shows Oxidation state -2 in Oxides, -1 in peroxides while +2 in oxygen difluoride. Since it does not have vacant d-orbital it doesn't show higher oxidation states while other elements of group 16 shows +2, +4  and +6 Oxidation states. 

4. Nature of Hydrides: The hydride of Oxygen H2O in a liquid while the Hydrides of other elements are gases. 

5. Covalency: Common Covalency of Oxygen is 2. rarely it is 4. But for other members of group 16 covalency can exceeds four.