[Korokian]

help please

Which of the following TWO facts represent evidence for the extra stability of a half filled sublevel?

W.  Chromium has valence shell electron config of 4s1 3d5
X. Oxygen has a lower ionization energy than nitrogen
Y. Aluminum has a lower ionization energy than magnesium.
Z. Neon has a higher ionization than fluorine

i believe x is correct, and w is incorrect
i do not know if y and z is true, they're not half filled sublevels

and

Which of the choices does each of the two elements have exactly four valence electrons?

A) Nb and Ag
B) Pb and Cu
C) Sn and V
D) C and As
E) Si and Zr

i do not think any pair has four valence electrons each

[Bakegaku]

I think you're misreading both questions.

The first one is asking which of the statements are supporting the fact that half-filled subshells are more stable (all the statements are true, but not all support this fact).  the answer of this question will be two letters (I.E. "X and Z"... not necessarily the right pair)

The second questions is asking which out of the pair given has 4 valence electrons, not which pair has both elements with 4 electrons.  The answers to these questions will be one of the elements in the pair for each letter.

[Korokian]

so X and Y for the first one

and B and C can fit for the 2nd one

[constant thinker]

Why do you say "Y" for the first one?

I see why you say "X" because N has a half filled 2p sublevel, and that statement is saying that it will take more energy to remove an electron from N than it will to remove an electron from O which has a more than half filled 2p sublevel.

[Korokian]

i actually change my answer, not Y, but W
Cr with a half filled s and p sublevel
because if Cr were 4s2 then the 3d4 electrons would get pushed further out due to repulsions in the the orbitals

[Bakegaku]

i actually change my answer, not Y, but W
Cr with a half filled s and p sublevel
because if Cr were 4s2 then the 3d4 electrons would get pushed further out due to repulsions in the the orbitals

Yes, W and X are what I'd choose for the first one.

The second one is basically 5 different questions.  For each one you give an answer.  For question A, the question is which has 4 valence electrons: Nb or Ag.  Then you would answer B, C, D  and E the same way. 

I suggest reading each question thuroughly more than once each time.  It can sometimes hurt a lot to misinterpret what it's asking.

[constant thinker]

W and X are what I'd also choose for the first one. That's why I asked you why you chose "Y".

I didn't common on the 2nd question because it's an odd question (as far as interpretation goes). I'm thinking that bakegaku is right on the interpretation of it.