Consider the electron configuration: 1s22s22p63s23p5 How many electrons are on the third energy level? O 4

O 7

O 2

O 8

There are 7 electrons on the third energy level

The maximum number of electrons that can be filled in the nth electron shell is 2n²(n=shell)

•K shell (n = 1) maximum 2 x 1² = 2 electrons  

•L shell (n = 2) maximum 2 x 2² = 8 electrons  

•M shell (n = 3) maximum 2 x 3² = 18 electrons  

•N shell (n = 4) maximum 2 x 4² = 32 electrons  

Electron configuration of Si : 1s²2s²2p⁶3s²3p⁵ = 17 electron

The electron distribution :

K shell(n=1) ⇒the first energy level= 2  

L shell(n=2) ⇒the second energy level= 8

M shell(n=3)⇒the third energy level = 7

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