Question

electron configuration and noble gas notation
what is the correct electron configuration for chlorine, atomic number 17?
o $1s^{2}2s^{2}2p^{6}3s^{2}3p^{5}$
o $1s^{2}2s^{2}2p^{6}3s^{2}3p^{3}$
o $1s^{2}2s^{2}2p^{6}3s^{2}$
o $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}$

Explanation:

Step1: Recall electron - filling order

Electrons fill orbitals in the order 1s, 2s, 2p, 3s, 3p, etc. The s - orbital can hold a maximum of 2 electrons, and the p - orbital can hold a maximum of 6 electrons.

Step2: Calculate electrons for chlorine

Chlorine has an atomic number of 17, which means it has 17 electrons.

Step3: Fill the orbitals

1s orbital is filled first with 2 electrons (1s²). Then 2s orbital is filled with 2 electrons (2s²). Next, 2p orbital is filled with 6 electrons (2p⁶). After that, 3s orbital is filled with 2 electrons (3s²). Finally, the remaining 5 electrons go into the 3p orbital (3p⁵). So the electron - configuration is 1s²2s²2p⁶3s²3p⁵.

Answer:

1s²2s²2p⁶3s²3p⁵