where can I find lewis dot formulas or vsepr models for:?

Question

Okay, so I want to know where I can find out what the lewis dot or vsepr model for the following molecules:

RnF2
SiI42- that's Silicon Iodide with a subscript 4 and then superscript 2-
KrO3
AlCl4-

Or if you know how to do the lewis dot structures, then that would be really great or if you can explain them to me would be just as good. thank you

Answer 1

SiI4 2- is not the formula of any real species.

RnF2: Rn has 8 outer electrons (from position in periodic table), F needs 8 round it and has 7. So each F shares a pair of electrons with Rn, one from each atom, making two Rn:F (Lewis pair) bonds. Rn has 3 lone pairs left over; so we have 5 pairs round Rn; two bonds and 3 lone pairs.

The 5 spread out as much as possible. That gives you a trigonal pyramid (the shape should be in your textbook). Because lone pairs are more repulsive than bond pairs, they occupy the three equatorial positions, while the bonds to F are top and bottom.

KrO3: O makes a double bond. So of the 8 electrons round Kr, 6 are involved in bonds and you have one lone pair. This gives you 4 "things" round the Kr, which spread out as much as possible, roughly into a tetrahedron. Lone pair in one corner, Kr in the middle, O atoms in each of the other 3.

Principles: set up your bonds. Count your total things rond the central atom (bonds and lone pairs). Spread out. Lone pairs take up more room than bonds.

It's not difficult but it DOES take practice.

I hope this helps.

Answer 2

Draw two H with an S in the middle. Then place two dots at positions (of a clock) at 12, 3, 6, and 9 respectively. H only needs to share 2 dots (electrons) to be satisfied. It is an exception to the octet rule.