Question

When “4p' orbitals in any atom are filled
completely the next electron goes in 5s​

Answer 1

This is because of Aufbau principle

According to Aufbau principle , Orbital with a lower (n-l) value is filled first

for 4p , n=4 , l=1
therefore n+l => 5

now we may think the next orbital must be 4d however for 4d , n+l value ==> 4+2 ==> 6

At the same time for 5s , it is simply 5+0 ==> 5

as 5< 6
the 5s orbital is filled first //