Question

Which of the following is not a stable ion?

1- Mg2+
2- S2-
3- CI-
4- K2+

which of the following is an example of an anion?
1- Na+
2- Fe
3- O2-
4- Ne​

Answer 1

#1

K^2+

How?

• K has Atomic number 19

Let's look at electronic configuration

`\\ \sf\longmapsto 1s^2s^22p^63s^23p^64s^1`

• 2+ charge means 2 electrons donated.

New EC will be

`\\ \sf\longmapsto 1s^22s^22p^63s^23p^5=[Ar]^-`

Hence its not stable .

#2

Anion means minus charge

Hence our answer is O^2-