Question

A neutral atom has a total of 17 electrons. The electron configuration in the outermost principle energy level will look closest to:

• A. $1s^2,2s^2,2p^5$
• B. $3s^2,3p^5$
• C. $s^2,p^5$
• D. $s^2,p^8,d^7$
• E. $s,p^7$

Answer 1

The correct option is B $3s^2,3p^5$

Neutral atom having 17 electrons is $Cl$ atom.
In writing the electron configuration for Chlorine the first two electrons will go in the 1s orbital. Since 1s can only hold two electrons the next 2 electrons for Chlorine go in the 2s orbital. The next six electrons will go in the 2p orbital. The p orbital can hold up to six electrons. We'll put six in the 2p orbital and then put the next two electrons in the 3s. Since the 3s if now full we'll move to the 3p where we'll place the remaining five electrons. Therefore the Chlorine electron configuration will be $1s^{2}2s^{2}2p^{6}3s^{2}3p^5.$