Question

why first ionisation energy less than 2nd IE?

Answer 1

The first ionisation energy removes the electrons from a neutral atom while the second ionisation energy removes electrons from a positive atom. The electrons are tightly bound by the positive atom due to increased attraction force, therefore the second ionisation energy is higher than the first.

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Answer 2

Solution

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Verified by Toppr

The second ionization energy of alkali metals are higher than first ionization energy is due to following reason.

1.The electrons configuration of M

+

ions is ns

2

np

6

i.e., stable noble gas configuration.

2.The size of M

+

ions is smaller due to increase in nuclear size.