Question

8.

a) Draw the most probable Lewis structure when one phosphorus, one selenium and one silicon combine. The overall charge is -1 (an anion)?

b) For your structure drawn in part A, are there any resonance structures?

c) Is your compound polar or non -polar?

d)What is the hybridization of the central element in your drawn structure?

Answer 1

A) Remember that the least electronegative element is the central atom.

Also remember that you have to calculate the formal charges and find the one closest to zero.

FC = number of group - (number of bonds + number of unshared electrons)

P = 5 - (3+2) = 0

Si = 4 - (4+0) = 0

Se = 6 - (1+6) = -1

This means that you have to have a triple bond in order that Si completes its octet

B) Resonance

If you consider that Se has a triple bond then you have the following charges

P = 5 - (1+6) = -2

Si = 4 - (4+0) = 0

Se = 6 - (3+2) = 1

This is not probable because is not the closest to zero.

On the other hand, if you consider the following structure

Then:

P = 5 - (2+4) = -1

Si = 4 - (4+0) = 0

Se = 6 - (2+4) = 0

C)

Calculate the difference of electronegativities and use the criteria:

• 0 - 0.04 is non polar
• 0.04 - 1.7 is polar
• 1.7 and above is ionic

P-Si = 2.19-1.9 = 0.29

Si-Se =2.55-2.19 = 0.36

Since you have opposite forces (because Se and P have different electronegativities having an effect on Si)

Total = 0.36 - 0.29 = 0.07

The compound is polar.

D)  

The hybridization is sp