Asingle atom of an element has 11 protons, 11 electrons, and 12 neutrons. which element is it?
a. v
b. na
c. mg
d. se

A. V is Vanadium and it has 23 electrons, so it couldn't be your answer.
B. Na is sodium and has 11 electrons, so it is your answer
C. Mg is Magnesium and it has 12 electrons, so it couldn't be your answer either.
D. Se is Selenium and it has 34 electrons, so it couldn't be your answer.
So your answer is B.