Why the electron after 6s1 and 6s2 enters 5d instead of 4f which is in accordance with the aufbau principle?

Asked by ashwinikumar59 | 24th Sep, 2010, 08:48: AM

Expert Answer:

 lanthanum has outer shell electronic configuration as 5d1 6s2 rather than expected beacuse as we go far from's' orbital to 'f' orbital, energy gap between d' and 'f' is very less, hence aufbau principle get disobeyed in these elements because of negligible energy difference. 

Answered by  | 24th Sep, 2010, 10:44: AM

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