CBSE Class 12 Chemistry P Block Elements Board Exam Notes

The general valence shell electronic configuration of p‐block elements ‐ ns2 np1–6


1. O, S, Se, Te and Po are present in G‐16th Their general electronic conf. of last shell is ns2,np4.
2. Atomic and ionic radii increases down the group while ionization enthalpy and electro-negativity decreases with increase in atomic number.
3. Because of compact nature of oxygen atom, it has less negative electron gain enthalpy than sulphur. However from sulphur onwards the value again becomes less negative up to polonium..
4. Members of group 16 show oxidation number ‐2, +2, +4 and +6. But oxygen shows +1 state in O2F2.
5. They make MO2 and MO3 type oxides. SO2 is reducing agent whereas TeO2 is oxidizing agent.
6. O2 is gas a n d other elements are solid.
7. O2 and S2 in vapour state are paramagnetic.


CBSE Class 12 Chemistry P Block Elements Board Exam Notes


1) Sulphur has more tendency to show catenation than oxygen
Ans.) Due to stronger S‐S bond and due to small size and greater interelectronic repulsion O‐O bond is weakened so it can't show catenation.
2) Oxygen is a gas but sulphur is a solid .

CBSE Class 12 Chemistry P Block Elements Board Exam Notes-1


4.) H2S is more acidic than H2O
Ans.) Bond dissociation enthalpy of S‐H bond is lesser than O‐H bond due to bigger size of sulphur.
5.) OF6 compound is not known, why?
Ans.) Due to the absence of d‐orbital in oxygen, it can't make OF6.

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