[lilmul123]

1. Why does sulfur have a lower ionization energy than chlorine?  I believe it has something to do with nuclear charge, but I'm not positive.

2. How many d electrons are present in Cu 2+?  I put 7 as my answer, but that is incorrect.  My thinking was that the 2+ charge got rid of 2 d electrons, taking it from 9d to 7d. 

3. Which of these elements, as a neutral atom, would have an electronic configuration influenced by the increased stability of a filled or half-filled subshell?  Zn only; Cr only; Cr and Cu; Cu only; Zn and Cr.

This one is hardest of all for me.  I believe that a filled subshell increases stability, but afaik, none of these have filled subshells.  I actually believe the trouble I'm having with this concept is that I simply don't remember everything exactly.  Thanks in advance for the help.

[enahs]

3 (&2)
Zn does have a filled sub-shell.

If you recall your Hunds rule, you place electrons in orbitals unpaired before you start pairing them. Electrons repeal each other, and by keeping them separated, it is more stable.

The valence S and D orbitals are of similar energy, and as a result it is fairly easy to promote an electrons from the 4s orbital into the 3d orbital. This allows the s orbital more stability by being unpaired; however it can not do this whenever it wants to; only when it makes the system overall more stable. This occurs when by promoting one of the s electrons into a d orbital makes the d orbital either completely filled or half-filled.

Thus for your Question 2, Cu actually is 4s¹3d¹⁰, because a filled shell and a half filled shell is more stable then a completely filled shell and a 9/10th filled shell.

And now you should be able to answer question 3; so what is the correct answer?


Your one, you are close. It is due to an increase in effective nuclear charge.
http://en.wikipedia.org/wiki/Effective_nuclear_charge


You should review in your book the whole section about the electronic configuration of atoms.

[vhpk]

Sulfur of course must have ionization energy lower than chlorine because in a cycle, ionization energy increases in the increasing of nuclear charge, this can explain by the configuration