CBSE Class 10 Science 2022 · Paper 31/6/1 · Question 1

Carbon and its Compounds 2 marks Medium

Draw the electron dot structure of the molecules of

(a)Oxygen, and
(b)Nitrogen. The atomic numbers of oxygen and nitrogen are 8 and 7 respectively.

Answer

$O_{2}$ has a double bond (two shared pairs); $N_{2}$ has a triple bond (three shared pairs); every atom has eight electrons.

(a) Oxygen,

O_{2}

: each O atom (2, 6) has six valence electrons and needs two more, so the two atoms share two pairs of electrons, a double bond,

O = O

. In the electron dot structure the two shared pairs sit between the two O symbols and each O keeps two lone pairs, so each O is surrounded by

4 + 4 = 8

electrons. (b) Nitrogen,

N_{2}

: each N atom (2, 5) has five valence electrons and needs three more, so the two atoms share three pairs of electrons, a triple bond,

N \equiv N

. The three shared pairs sit between the two N symbols and each N keeps one lone pair, so each N is surrounded by

2 + 6 = 8

electrons. The figure shows both structures, with one atom's electrons as dots and the other's as crosses.

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