What is the electron configuration of chlorine (CI)? 1s22s s23p3
1s22s22p 3s 3p5
1s22s22p3s24s23p3
1s22s 23d

1s²2s²2p⁶3s²3p⁵

Explanation:

Please see attached picture for working. (Answer using periodic table)

(See 2nd picture)

Alternatively, we can look at the subshell filling sequence.

Chlorine has 17 electrons.

So we start by filling the subshell with the lowest energy level, 1s.

The s subshell can fill a maximum of 2 electrons.

So what we have now is 1s²... with 15 electrons left.

Next, we look at the 2s subshell. Again, it can fill a maximum of 2 electrons.

1s²2s²... and we have 13 electrons left.

Moving on to the 2p subshell. The p subshell has 3 orbitals so it can fill a maximum of 6 electrons.

1s²2s²2p⁶... and we have 7 electrons left.

For the 3s orbital, it can fill another 2 electrons.

1s²2s²2p⁶3s²... 5 electrons to go!

Look at the 3p subshell. It can fill 6 electrons.

1s²2s²2p⁶3s²3p⁵

and we have obtained the electronic configuration of chlorine!

the answers would be

the first one and the second one