Molecular Orbitals

Question 1

What can orbitals be used to explain?

Answer 1

The bonding between atoms

Question 2

What are atomic orbitals?

Answer 2

The volume of space that the electron of an atom is likely to be found

Question 3

What happens when atomic orbitals overlap?

Answer 3

They combine to form molecular orbitals

Question 4

What are sigma bonds?

Answer 4

The end on overlapping of orbitals

Question 5

What governs the type of intermolecular bonding?

Answer 5

The shape of the molecular orbital

Question 6

How are non-polar bonds formed?

Answer 6

When two atoms of the same element bond

Question 7

What can be said about the molecular orbitals formed in non-polar elements?

Answer 7

The molecular orbital formed from overlapping atomic orbitals is symmetrical around a mid-point where the bonding electrons are most likely to be found

Question 8

What is a polar covalent bond?

Answer 8

When there is a large difference between the electronegativities of the two elements involved in the bond

Question 9

What can be said about the molecular orbits in polar covalent bonds?

Answer 9

The bonding molecular orbitals will be asymmetrical

Question 10

What happens when ionic bonds form?

Answer 10

There is extreme asymmetry

Question 11

What does hybrid theory assume?

Answer 11

That the 2s and 2p orbitals of carbon atoms combine to form four degenerate orbitals

Question 12

What are the hybrid orbitals formed from 1 s orbital and 3p orbitals called?

Answer 12

They are called sp³ orbitals

Question 13

What happens in alkanes?

Answer 13

All four hybrid orbitals are used to form sigma bonds

Question 14

What can be said about sigma bonds?

Answer 14

They allow free rotation around orbitals

Question 15

How are C-C bonds in alkanes formed?

Answer 15

From the overlapping of sp³ orbitals forming sigma bonds

Question 16

How many sigma bonds are in ethane?

Answer 16

7

Question 17

What does an electron being promoted to higher energy levels result in?

Answer 17

The formation of 3 hybrid orbitals, with one remaining unhybridised 2p orbital

Question 18

What is bonding in alkanes due to?

Answer 18

hybridisation

Question 19

What are the hybrid orbitals from one s orbital and two p orbitals called?

Answer 19

sp² orbitals

Question 20

What is the angle between sp² orbitals?

Answer 20

120 degrees

Question 21

What is a pi bond?

Answer 21

The sideways overlap of two parallel atomic orbitals

Question 22

What is the comparison between sigma and pi bonds?

Answer 22

Pi bonds are weaker than sigma bonds

Question 23

What bonding orbitals are present in C-C bonds?

Answer 23

1 sigma bond

Question 24

What bonding orbitals are present in C=C bonds?

Answer 24

1 sigma and 1 pi

Question 25

What bonding orbitals are present in C≡C bonds?

Answer 25

1 sigma and 2 pi

Question 26

What are isomers?

Answer 26

Molecules with the same chemical formula but different structural formula

Question 27

What can be said about structural isomers?

Answer 27

They have different physical and chemical properties

Question 28

What are the two types of stereoisomerism?

Answer 28

* geometric isomerism | * optical isomerism

Question 29

What is geometric isomerism a result of?

Answer 29

A lack of rotation around a bond

Question 30

What is a cis isomer?

Answer 30

cis means the functional group is on the same side of the C=C

Question 31

What is a trans isomer?

Answer 31

When the functional group is on opposite sides of the C=C bond

Question 32

Why do trans isomers have higher mpts?

Answer 32

As these molecules can pack more closely together thus maximising the intermolecular forces

Question 33

Why do cis molecules have higher bpts?

Answer 33

Because of their PD-PD interactions

Question 34

What are the types of geometric isomerism?

Answer 34

* cis isomerism | * trans isomerism

Question 35

Why are cis isomers more readily dehydrated than trans isomers?

Answer 35

because of the close proximity of the OH groups

Question 36

What are optical isomers?

Answer 36

They are mirror images of each other but are not superimposable

Question 37

What does a tetrahedral molecule have the potential to be?

Answer 37

chiral

Question 38

How does chirality occur?

Answer 38

when the middle atom is attached to four different groups

Question 39

What does a polariser allow?

Answer 39

Light vibrating in only a single plane to pass through them

Question 40

What are enantiomers?

Answer 40

Another term used to describe optical isomers

Question 41

What is a racemic mixture?

Answer 41

One which contains equal amounts of each enantiomer

Question 42

What type of hybridisation is present in alkynes?

Answer 42

sp hybridisation

Question 43

What type of hybridisation is present in alkenes?

Answer 43

sp² hybridisation

Question 44

What type of hybridisation is present in alkanes?

Answer 44

sp³ hybridisation

Question 45

What does the combination of two atomic orbitals result in?

Answer 45

the formation of a bonding and an antibonding orbital

Question 46

When electrons fill bonding molecular orbitals, what do they leave behind?

Answer 46

Higher energy antibonding orbitals unfilled

Question 47

How many groups are changed in enantiomers ?

Answer 47

Only 2.