1s²2s²2p⁶3s²3p⁵
Step-by-step explanation:
In writing the first two electrons will go in the 1s orbital.
Since 1s can only hold two electrons the next 2 electrons for chlorine go in the 2s orbital.
The next six electrons will go in the 2p orbital.
The p orbital can hold up to six electrons.
We'll pull six in the 2p orbital and then put the next two electrons in the 3s.
Since the 3s is now full we'll move to the 3p where we'll place the remaining five electrons.
Hope this helped ;)