Neon has 10 protons and 10 electrons. How many additional electrons would it take to fill the outer (second) electron shell?

Feb 16, 2017

zero!

Explanation:

Neon is a noble gas. The noble gasses all have filled outer electron shells.

Put another way, the number of electrons that can be put in any shell is $2 {n}^{2}$ so, for the n=1 shell you get $2 \times {1}^{2}$ or 2 electrons. for the n=2 shell you get $2 \times {2}^{2}$ or eight electrons.

$2 + 8 = 10$

That's neon.