simple chem: why [kr]5s1 4d10 and not [kr] 5s2 4d9?

Question

Thank you guys so much. Chemistry is a nightmare (and only 2.5 weeks in...). Why does it fill "d" before "s" (I though "s" was filled first)?
Thanks in advance to anyone who can solve my petty, trival problems. ^_^

Answer 1

look it this way....
in [kr]5s2 4d9 the electrons in the d orbital is only 9 and thus there is one orbital that is not completely filled up. the "extra" electron, i.e. the ninth electron will cause some sort of electronic repulsion thus it will become less stable (Review the Hund's rule of multiplicity)
on the other hand, if the electronic configuration is to be written as [kr] 5s1 4d10 no electronic reppulsion will be observe in both orbitals, in the s orbital there is only one electron and thus no electronic repulsion. for the d orbital, it is completely filled-up and thus relatively stable (Hund's rule of multiplicity)

best answer?

Answer 2

It is energetically favorable to have 10 d electrons, more so than having a full s orbital (2 electrons) and missing one d electron (9). Just memorize the few examples that are exceptions, there are only a couple.

It is not worth it to try to think about the orbitals and why the d orbital is favored to be filled over the s if you are only learning electron configurations. It will only make you hate chemistry.

Chemistry is very useful...I hate how they teach you the most boring things and don't mention any practical uses.

Answer 3

the d orbitle is fullfilled with all the 10 electrons thus more stable configuration is attained n thus it goes by this way best of luck

Answer 4

It takes more energy to fill the "d" orbital than it does the "s" orbital.