Question

the partial electron configuration of an atom with 12 electrons is shown. 1s²2s²2p⁶x. which of the following does x represent? 2d² 3s² 3p² 4s²

Explanation:

Step1: Calculate electrons in given configuration

The given partial - electron configuration is $1s^{2}2s^{2}2p^{6}X$. The number of electrons in $1s^{2}$ is 2, in $2s^{2}$ is 2, and in $2p^{6}$ is 6. So the total number of electrons in $1s^{2}2s^{2}2p^{6}$ is $2 + 2+6=10$.

Step2: Determine remaining electrons

The atom has 12 electrons in total. After accounting for 10 electrons in $1s^{2}2s^{2}2p^{6}$, the number of remaining electrons is $12 - 10 = 2$.

Step3: Identify the next sub - shell

According to the Aufbau principle, after the $2p$ sub - shell, the next sub - shell to be filled is the $3s$ sub - shell. And since we have 2 remaining electrons, the configuration of $X$ is $3s^{2}$.

Answer:

$3s^{2}$