Question

anamolous behaviour of oxygen​

Answer 1

Answer:

Anomalous behaviour of oxygen

Oxygen forms strong hydrogen bonding in H2O which is not found in H2S. Also, the maximum covalency of oxygen is four, whereas in a case of other elements of the group, the valence shells can be expanded and covalency exceeds four.

Reasons for the anomalous behaviour of oxygen are:

• Small size and high electronegativity

• Absence of d-orbitals

Reactivity towards hydrogen: All the elements of Group 16 form hydrides of the type H2E (E = S, Se, Te, Po).

Thermal stability: Thermal stability of group 16 elements decreases down the group.

H2O > H2S > H2Se> H2Te > H2Po

This is because the H-E bond length increases down the group, hence the bond dissociation enthalpy decreases down the group.

Acidic nature: Due to the decreasing bond dissociation enthalpy, acidic character of group 16 elements increases down the group.

H2O < H2S < H2Se < H2Te

Reducing character: The reducing character also decreases down the group due to the decreasing bond dissociation enthalpy.

H2O < H2S < H2Se < H2Te < H2Po

Reactivity towards oxygen: All group 16 elements form oxides of the type EO2 and EO3 Reducing character of dioxides decreases down the group. Acidity also decreases down the group. Besides EO2 type, sulphur, selenium and tellurium also form EO3 type oxides. Both types of oxides are acidic in nature.

Reactivity with halogens: Elements of Group 16 form a large number of halides of the type, EX2 EX4 and EX6, where X is a halogen. The stability of halides decreases in the order F− > Cl− > Br− > I− . This is because E-X bond length increases with increase in size. Among hexa halides, hexafluorides are the most stable because of steric reasons. Dihalides are sp3 hybridised and have tetrahedral geometry. H2O is a liquid while H2S is a gas. Because in water due to the small size and high electronegativity of O, strong hydrogen bonding is present there.

Oxygen (O)

Oxygen is the first element of Group 16 with the electronic configuration of 1s2 2s2 2p4 in the ground state. Oxygen has two allotropes: dioxygen (O2) and trioxygen or ozone (O3).

Dioxygen (O2)

Oxygen usually exists in the form of dioxygen.

Preparation:

Dioxygen is prepared in the laboratory by thermal decompositions of oxygen rich compounds such as KClO3,

Answer 2

Answer:

1. oxygen shows anomalous behavior due to formation of double π-bond
2. small size
3. high electro negativity

Explanation:

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