Question

Which rule is violated in the electronic configuration 1s0 2s2 2p4?

Answer 1

In the above electronic configuration Aufbau principle is violated.

(n + l) value of 1s is 1 + 0 = 1

(n + l) value of 2s is 2 + 0 = 2

Here electrons are filled in 2s orbital, without filling 1s orbital which has lower (n + l) value than 2s. Hence Aufbau principle is violated.