if atomic number is 26 than electronic configuration would be 1s2s2p3s3p3d
there are two electrons in 1s
two electrons in 2s
six electrons in 2p
two electrons in 3s
six electrons in 3p
eight electrons in 3d
valence electron is 3 so 3s3p3d = 2+6+8
=16 electrons in valence shell
