Wrong electronic configuration
a. 1s2 , 2s2 , 2p7 (2p maximum 6 electrons only)
c. 1s2 , 2s2 , 2p5 , 3s1 (electrons are filled in 3s only after filling 6 electrons in 2p)
d. 1s2 , 2s2 , 2p6 , 3s2 , 3p6 , 3d2 , 4s1 (electrons are filled in 3d only after filling 2 electrons in 4s)