Periodic Classification and Periodic Properties 2 Question 28
28. The first ionisation potential of nitrogen and oxygen atoms are related as follows.
$(1989,1 \mathrm{M})$
(a) The ionisation potential of oxygen is less than the ionisation potential of nitrogen
(b) The ionisation potential of nitrogen is greater than the ionisation potential of oxygen
(c) The two ionisation potential values are comparable
(d) The difference between the two ionisation potential is too large
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Answer:
Correct Answer: 28. (a)
Solution:
- (a) and (b) are infact the same statements and both are correct. N has slightly greater ionisation energy than oxygen which is against periodic trend. This exception is due to completely half-filled $\left(2 p^{3}\right)$ orbital in nitrogen that makes ionisation slightly difficult than oxygen.
(c) Also correct: Although $\mathrm{N}$ has greater first ionisation potential than oxygen, two values of ionisation potentials are comparable since they are adjacent in a period, i.e. electrons are removed from same orbit during ionisation.
(d) Incorrect - opposite to (c). of the bonded atoms which in turn has periodic trend in long form of periodic table.
