Shapes of molecules and Ions

Question 1

What are the 2 factors that dictate the shape of a compound or ion?

Answer 1

• The number of electrons pairs around the central atom
• The nature of electron pairs

Question 2

What are the 2 types of electron pairs

Answer 2

-Lone pairs
-Bonding pairs

Question 3

What are bonding pairs?

Answer 3

Pairs of electrons involved in bonding

Question 4

What are lone pairs?

Answer 4

Pairs of electrons not involved in bonding.

Question 5

Which electron pairs repels other pairs more, Bonding pairs or Lone pairs? And why?

Answer 5

Lone pairs repel other electron pairs more than bonding pairs do, and that’s because they are more electron dense

Question 6

By how much does each lone pair reduce the bond angle approximately?

Answer 6

By about 2.5°

Question 7

Are molecules 3D or 2D shaped?

Answer 7

3D SHAPED

Question 8

What is the octet rule?

Answer 8

atoms react with each other to form a full outer shell containing 8 electrons

Question 9

What does each line show:
-straight line
-bold wedge
-dotted wedge

Answer 9

-bond in the plane of the paper
-bond is coming out of the paper towards you
-bond is going into the paper away from you

Question 10

Is the octet rule ALWAYS achievable? Why?

Answer 10

No, sometimes atoms have less than enough electron bonding pairs and sometimes they have more than enough to form an octet

Question 11

What happens when there are not enough electrons to form an octet?

Answer 11

The octet is shrunk but the unpaired electrons will bond, but an octet will not be achieved

Question 12

What happens when there are more than enough electrons to form an octet?

Answer 12

octet is expanded and unpaired electrons will bond and more than 8 electrons will be in the outer shell

Question 13

How many bonding pairs are in a linear bond? what is an example?

Answer 13

1 pair or 2 pairs
hydrogen H2
CO2 (2 bonding pairs)

Question 14

What is the name of the molecular shape where there are 3 bonding pairs ? What is the angle between each atom?

Answer 14

Trigonal Planar
120*

Question 15

What is the name of the molecular shape where there are 4 bonding pairs ? What is the angle between each atom?

Answer 15

Tetrahedral
109.5*

Question 16

What is an example of tetrahedral shape?

Answer 16

CH4 methane

Question 17

What is the name of the molecular shape where there are 3 bonding pairs and 1 lone pair ? What is the angle between each atom in this shape?

Answer 17

Pyramidal
107*

Question 18

What is the name of the molecular shape where there are 2 bonding pairs and 2 lone pairs? What is the angle between each atom?

Answer 18

Non linear
104.5*

Question 19

example of non linear?

Answer 19

H2O

Question 20

example of pyramidal shaped molecule?

Answer 20

Ammonia Nh3

Question 21

What is the name of the molecular shape where there are 5 bonding pairs ? What is the angle between each atom?

Answer 21

Trigonal Bipyramid
90* between atoms in the same plane and 120 between atoms coming in and out of the page

Question 22

What is the name of the molecular shape where there are 6 bonding pairs ? What is the angle between each atom?

Answer 22

octahedral
90*

Question 23

What is the electron pair repulsion theory?

Answer 23

Electrons pairs repel each other, but lone pairs repel each other more than bond pairs repel each other

Question 24

Why can’t oxygen form OF6 like sulfur forms SF6?

Answer 24

since it cannot expand its octet