If an atom has twelve electrons, how many electrons are in the n=1 energy level? how many electrons are in the n=2 energy level? how many electrons are in the n=3 energy level?

Magnesium has 12 electronswhich wud mean that in the 1st energy level(n=1) there r 2 electrons, in the 2nd energy level(n=2) there r 8 electrons and in the 3rd energy level(n=3) there r 2 electronsits simpleuse the formula 2n^2 where n= 1,2,3,  

so the electron configuration of Magnesium in 2,8,2or more precisely 1s2, 2s2, 2p6, 3s2

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