Question

Why is the second ionization energy greater than the first ionization energy in atoms?

Answer 1

`M(g) + Delta_1 rarr M^(+)(g) +e^-` `"1st ionization energy"`

`M^(+)(g) + Delta_2 rarr M^(2+)(g) +e^-` `"2nd ionization energy"`

Explanation:

Let's look at the process purely on the basis of electrostatics. It should take more energy to remove an electron from a positively charged atom, than from a neutral atom, because the valence electrons of a positive species should be more strongly attracted to the nuclear core, and shielding of the nuclear charge by electrons should diminish.

On this basis alone, `Delta_2>Delta_1`.

In the special case of the alkali metals, the second ionization energy would involve the removal of a non-valence, inner shell electron. And thus, in this instance, `Delta_2` should be PROHIBITIVELY HIGH.....

Are the given data consistent with what we have argued? Why is a second ionization energy not listed for hydrogen?