Question

The second ionization enthalpy of alkaline earth metals is greater than the first ionization enthalpy, yet they form +2 ions. Explain.​

Answer 1

Answer:

The reason for this is Alkaline earth metals are group 2. They have 2 electrons in the outershell. Both these electrons are in the same s orbital and they are approximately the same distance from the nucleus. So they have electrostatic attraction and about the same energy. Though, the first electron removed requires less energy because there is a slight shielding effect caused by the other electron in the same orbital.

An alkali metal is period 1. It only has 1 electon in the outer shell. So the second electron which is removed will be from the p orbital of the shell n-1. The shell n-1 is closer to the nucleus than the n shell, therefor it has a strong electrostatic attraction to the nucleus, which requires more energy to remove.