Shapes of simple molecules and ions

Question 1

How to determine the shape of a molecule?

Answer 1

1. Add the central group atom
2. Add the number of molecules bonding to the central atom
3. Add or takeaway the charge
4. Then divide by 2
5. Then find the difference between the bonding pairs and the sum of 1+2+3 to find the number of lone pairs.

Question 2

Names and bond angles of molecule shapes

Answer 2

Linear - 2 bp/0lp = 180 degrees

Bent - 2bp/2lp = 104.5

Trigonal Planar - 3bp/0lp = 120 degrees

pyramidal - 3bp/1lp = 107 degrees

Tetrahedral 4bp/0lp = 109.5 degrees

Trigonal Bipyramid - 5bp/0lp = 90 and 120 degrees

Octahedral - 6bp/0lp = 90 degrees

Question 3

What happens to the electrons in the outer shell?

Answer 3

Pairs of electrons in the outer shell of atoms arrange themselves as far apart as possible to minimise repulsion.

Question 4

Which repulsion is stronger: lone pair-lone pair or lone pair-bond pair?

Answer 4

Lone pair-lone pair repulsion is greater.

Each lone pair reduces the bond angle by 2.5 degrees.

Question 5

EQ: Which species has a lone pair of electrons on the central atom?

Answer 5

Answer: B

Question 6

Answer 6