# Lone pairs on central atom

1. Oct 30, 2006

### lorka150

I have to figure out which has two lone pairs on the central atom between PCl3, ICl4^+, CH3I, XeF4, PCl6^-.

Is it PCl3? I think I did it right but I am not sure.
Thank you.

2. Oct 30, 2006

### Smith4046

Think you are correct. The three 3p3 electrons of P should be bonded to the three Cls, each one forming single bonds. That leaves the pair of 3s2 electons unshared. Haven't even looked at the other choices, since I feel PCl3 is the one.

If incorrect, please someone let me know.

Best of luck.

Steve

3. Oct 30, 2006

### lorka150

hi Steve, thanks.
I re-checked my answer and realize I think I read the question wrong... Two lone pairs, meaning four all together (I was interpreting it like two, not two pairs) if that makes sense. Then I think it's XeF4.

4. Oct 30, 2006

### geoffjb

The bonds are not strictly s and p bonds, but rather are spd hybridized.

$PCl_{3}$ has only one lone pair. So, you can rule it out.

Carbon must obey the octet rule, so you can rule out iodomethane.

Try drawing Lewis structures for the other 3. One is square planar (octahedral), thanks to its two lone pairs.

Last edited: Oct 31, 2006