Question

I get that in the first shell there are 2 electrons and then 8 in the next, but when can an atom have more that 8 electrons in its shells?

Answer 1

In its third shell or more.

Explanation:

A simple rule to follow, is that if `n` is the shell of an electron (energy level), it can hold a maximum of `2n^2` electrons.

So, we can setup an equation to show this:

`2n^2>8`

`n^2>4`

`n>2` (since `n>0`)

So, after the second shell, the atom can hold more than `8` electrons.

Source:

https://en.wikipedia.org/wiki/Electron_shell