Unpaired electrons (Homework 2.51) [ENDORSED]

[mitalisharma2B]

Would elements in the 5d group have 9 electrons instead of 10?

For instance, homework problem 2.51 asks how many unpaired electrons reside in the predicted ground state electron configuration for Tantalium.
Would the answer to this be 2 unpaired electrons or 3 unpaired electrons?

[Seth_Evasco1L]

Elements that have the 5d orbital can have up to 10 electrons in that specific subshell (I get that it's confusing since that's when the "f" orbitals begin to show up). Tantalum's electron configuration is [Xe]4f¹⁴5d³6s² so it would have three unpaired electrons found in the 5d orbital.

[sandros]

According to Hund's rule, orbitals of the same energy are each filled with one electron before filling any with a second. Also, these first electrons have the same spin. (wikibooks.org)
Since we have 5 different orbitals for d then we can have up to 5 unpaired electrons. Therefore, the correct answer would be 3 unpaired electrons.

Hope this helps.

[Chem_Mod]

These are correct above. I believe the confusion lies in the periodic table you use. Take a look at the periodic table on the boards the next time you are in class, and you will see there are in fact 10 elements, and therefore 10 electrons, in the 5d row. In some periodic tables, such as the one passed out during the first quiz, La and Ac are in the bottom "f-block" area when in fact they are in the "d-block" area. Take a closer look, count the elements, and hopefully that helps clear up any confusion!