Question

How many electrons are needed to completely fill the orbitals from 1s to 4p?

Answer 1

From 1s to 4p, the arrangement looks like that:

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p.

s contains 2 electrons
p contains 6 electrons
d contains 10 electrons

So, total electrons from 1s to 4p =36 electrons