lewis structures and shapes of molecules

Question 1

what are the 3 exceptions to the octet rule ?

Answer 1

radicals (odd number of electrons)
electron poor molecules (less electrons than an octet)
more electrons than an octet

Question 2

what is the equation for the formal charge

Answer 2

(number of valence electrons from the free atom) - (number of bonds to the atom) - (number of unshared electrons)

Question 3

what is the maximum CN for B, C, N

Answer 3

4

Question 4

what is the maximum CN for O

Answer 4

3

Question 5

what is the maximum CN for F

Answer 5

2

Question 6

what is the maximum CN for all of period 3

Answer 6

6

Question 7

what is the maximum CN for period 4,5,6

Answer 7

6,7,8

Question 8

what does hyper valence mean

Answer 8

when there are more than 8 valence electrons around the central atom

Question 9

why does NF5 not exist?

Answer 9

1. oxidation state of 5 is allowed.
2. however CN isn’t
3. due to the fact that the nitrogen atom is to small to have efficient overlap with more than four other atoms (ligands).

Question 10

draw a molecule with 3 bonds and 0 lone pairs

Answer 10

120

Question 11

draw a molecule with 2 bonds and 1 lone pairs

Answer 11

<120 for between the bonding pairs

> 120 for the lone and bonding pair

Question 12

draw a molecule with 4 bonds and 0 lone pairs

Answer 12

109 between top and right bonds

Question 13

draw a molecule with 3 bonds and 1 lone pairs

Answer 13

<109 between left and bottom bond

Question 14

draw a molecule with 2 bonds and 2 lone pairs

Answer 14

<109 between bonds

Question 15

draw a molecule with 5 bonds and 0 lone pairs

Answer 15

90 between left and bottom bonds, 120 between right bonds

Question 16

draw a molecule with 4 bonds and 1 lone pairs

Answer 16

<90 for top to next bond, <120 middle two, <90 to the bottom bond

Question 17

draw a molecule with 3 bonds and 2 lone pairs

Answer 17

<90 for left and bottom bond

Question 18

draw a molecule with 2 bonds and 3 lone pairs

Answer 18

no angles

Question 19

draw a molecule with 6 bonds and 0 lone pairs

Answer 19

90 between all bonds

Question 20

draw a molecule with 5 bonds and 1 lone pairs

Answer 20

<90 for top to higher left bond, 90 exactly for bottom left to higher left bond

Question 21

draw a molecule with 4 bonds and 2 lone pairs

Answer 21

90 between both bonds

Question 22

draw a molecule with 3 bonds and 3 lone pairs

Answer 22

<90 between two bonds on the left

Question 23

draw a molecule with 2 bonds and 4 lone pairs

Answer 23

no angles

Question 24

what is a super pair

Answer 24

a double bond, treat it as a single bond however increase the repulsion between other pairs

Question 25

VSEPR doesn’t work for …

Answer 25

transition metal complexes