The atomic number of chlorine is 17. Give the electron configuration for a neutral atom of chlorine

The neutral atom chlorine has an atomic number of 17 therefore it also contains a total of 17 electrons. We can write its ground state electronic configuration as 1s 2 2s 2 2p 6 3s 2 3p5

Additional info we can get here is that since the last one is 3p5 therefore its valence electron is 5.