Electron pairing in atoms

A question asks:



> 
> This question refers to isolated gaseous atoms. In which atom are all electrons paired? Ba, Br, S or Si?
> 
> 
> 


I thought it was Ba as its electron configuration is [Xe] 6s2.


However, the answer says Si, which seems incorrect to me.


Could someone please confirm the answer for me?


Thanks




The configuration for the free atoms is:


* Ba - $\mathrm{[Xe]\ 6s^2}$
* Br - $\mathrm{[Ar]\ 3d^{10} 4s^2 4p^5}$
* S - $\mathrm{[Ne]\ 3s^2 3p^4}$
* Si - $\mathrm{[Ne]\ 3s^2 3p^2}$


Thus:


* Barium has no unpaired electrons.
* Bromine has one unpaired electron in 4p subshell.
* Sulfur has two unpaired electrons in the 3p subshell.
* Silicon has two unpaired electrons in the 3p subshell.


 7