Question

step 2 fill in the subshells with the 8 electrons. list the subshells in order of lowest to highest energy. use the diagram of how subshell energy increases as a guide. each orbital can hold a maximum of two electrons. pairs of electrons have opposite spins, written as arrows pointing in opposite directions. each orbital in a subshell needs one electron before electrons are paired. step 3 write the electron configuration. list subshells in order of lowest to highest energy. write the number of electrons in each subshell as a superscript.

Explanation:

Step1: Fill lowest - energy subshells first

The first 2 electrons go to 1s subshell as it has the lowest energy. Each orbital can hold 2 electrons, so 1s is filled with 2 electrons with opposite spins ($\uparrow\downarrow$).

Step2: Fill next - lowest subshell

The next 2 electrons go to the 2s subshell which is the next in energy order. 2s also gets 2 electrons with opposite spins ($\uparrow\downarrow$).

Step3: Fill remaining electrons in 2p

We have 8 - 2 - 2=4 electrons left. According to Hund's rule, each of the three 2p orbitals gets one electron first with the same spin, and then the remaining electron pairs up with one of them. So the configuration of 2p is ($\uparrow\downarrow\uparrow\uparrow$).

Answer:

$1s^{2}2s^{2}2p^{4}$