How do you determine the number of electrons needed to fill the outer shell of an element?

1 Answer
Dec 25, 2017

2n^22n2

Explanation:

The number of valence electrons needed to fill its shell can be determined by inputting the shell level, n, squaring it, and by multiplying by 2.

  • Shell 1 holds 2 valence e^-e.
    2(1^2)=22(12)=2
  • Shell 2 = 8
    2(2^2)=82(22)=8
  • Shell 3 = 18
    2(3^2)=182(32)=18
  • Shell 4 = 32
    2(4^2)=322(42)=32
  • Shell 5 = 50
    2(5^2)=502(52)=50

You can decide whether you want to memorize the sequence in which each level can hold, "2, 8, 18, 32, 50, etc.," or you can remember this simple function of 2n^22n2 for a quick reference.