27. What element has this electron configuration: 1s2 2s22p6 352 3p6 452 3d10 4p4

Choices:
Sulfur
Selenium
Arsenic
Tellurium

Selenium

Explanation:

One way to figure this out is to count the electrons and add them up.

2+2+6+2+6+2+10+4 = 34 electrons

A neutral atom has the same number of electrons and protons. Protons tell us the atomic number of an element. Element number 34 is Selenium.

Another way to figure it out is to look at just the highest "s" or "p" level of the electron configuration, and then see which element corresponds to that. This element has a 4s and a 4p, so I will look at 4p. The configuration is 4p4, so I will look at the 4th row of the periodic table (4p4) in the "p" block (4p4) and the 4th element in the "p" block (4p4). That's selenium :)