Whenever there are 4 unpaired electrons in d-orbital, elements try to attain stable electronic configuration. For example copper.

Electronic configuration of copper should be [Ar]3d4 4s2, but it tries to attain stable state and so it changes to [Ar]3d5 4s1.

I have seen it happens with most of the elements but not with tungsten. Electronic configuration of tungsten is [Xe]4f14 5d4 6s2 and not [Xe]4f14 5d5 6s1(more stable).

What is the reason behind that?

  • 3
    $\begingroup$ If it was more stable, it would be adopted, so it isn't more stable. Anyway, the electronic configurations of the transition metals are often quite hard to rationalise, there are many factors that will tip the balance in favour of one configuration or another. $\endgroup$ Commented Nov 26, 2015 at 12:39
  • $\begingroup$ @orthocresol yeah that was my question why 5d4 is more stable then 5d5. Can you sate few factors that... I think you can add it as answer. $\endgroup$
    – Freddy
    Commented Nov 26, 2015 at 12:49
  • $\begingroup$ @jan not really. There is no where mention of tungsten configuration (at one place there is but that is not what I am asking,right?) $\endgroup$
    – Freddy
    Commented Nov 26, 2015 at 13:14
  • $\begingroup$ The basis of that question tells you that the electron configuration you termed ‘stable’ is, in fact, ‘abnormal’. So tungsten actually assumes the normal configuration. Thus, I consider it a duplicate. $\endgroup$
    – Jan
    Commented Nov 26, 2015 at 13:16
  • $\begingroup$ @Freddy Aesin's answer does give some mention to tungsten at the end. In general, the principles behind the effect are given in the linked question so the same answer applies here. $\endgroup$
    – bon
    Commented Nov 26, 2015 at 13:44