Q. Which one violates Aufbau principle ?

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Solution:

According to Aufbau principle increasing order of energy of various orbitals is
1s, 2s, 2p, 3s, 3p, 4s 3d, 4p, 5s, etc.
Therefore, Solution
is not obeyed by Aufbau principle. Without fully filling of s-subshell electron cannot goes p-subshell in ground state of atom.