Organic Chemistry 1.1 - Molecular Orbitals - MOs, Hybridisation, Sigma and Pi Bonding

Question 1

Molecular orbitals form when…

Answer 1

atomic orbitals combine

Question 2

Atomic and molecular orbitals can both hold a maximum of _ electrons.

Answer 2

2

Question 3

The ___ of molecular orbitals formed is ___ to the number of atomic orbitals that…

Answer 3

number, equal, combined/merged

Question 4

Molecular orbitals can be ___ or ___.

Answer 4

bonding or *antibonding

Question 5

Antibonding orbitals are represented by an _.

Answer 5

*

Question 6

The combination of two atomic orbitals results into the formation of…

Answer 6

a bonding and an antibonding molecular orbital.

Question 7

The bonding molecular orbital ___ both ___.

Answer 7

encompasses both nuclei.

Question 8

What is said to be the basis of atomic bonding?

Answer 8

the attraction between the +ve nucleus and the -ve electrons

Question 9

In a carbon atom the electrons are arranged like:
1s2, 2s2, 2p6.
If this is the case, how can carbon make 4 bonds?

Answer 9

Hybridisation occurs between the 2s and 2p orbitals

Question 10

Hybrid orbitals are formed through ___, and are a type of ___ ___.

Answer 10

Hybridisation, atomic orbital

Question 11

Describe what happens when the 2s and 2p orbitals hybridise.

Answer 11

the 4 atomic orbitals merge to form 4 degenerate hybrid sp3 orbitals.

Question 12

When atomic orbitals from different energy levels hybridise, they become…

Answer 12

degenerate (atomic orbitals on the same energy level are already degenerate)

Question 13

Why are these hybrid orbitals named sp3?

Answer 13

because of the one s and three p orbitals that combined to make them

Question 14

The numbers in hybrid orbital names refers to the number of… not the number of ___.

Answer 14

orbitals that hybridised to form them, electrons

Question 15

Molecular orbitals are ___ and can arrange themselves into shapes such as…

Answer 15

degenerate, tetrahedral, trigonal planar ect

Question 16

What is hybridisation?

Answer 16

hybridisation is the process of merging atomic orbitals within an atom to create a new type of atomic orbitals called hybrid orbitals, which are degenerate

Question 17

Hybrid orbitals are a type of ___ orbital.

Answer 17

atomic

Question 18

What is the difference between molecular and hybrid orbitals?

Answer 18

molecular orbitals are formed when atomic orbitals of two different atoms combine.
hybrid orbitals are formed when atomic orbitals within the same atom hybridise

Question 19

What is a Sigma bond?
What is a Pi bond?

Answer 19

the end-on overlap of two atomic orbitals of different atoms.
the side-on overlap of two atomic orbitals of different atoms.

Question 20

What is the symbol for sigma and pi?

Answer 20

σ, π

Question 21

Do all molecules need to hybridise to form bonds?

Answer 21

no

Question 22

The formation of a sigma or pi bond is synonymous with the formation of a ___ and an ___ molecular orbital.

Answer 22

bonding, antibonding

Question 23

A sigma bond is also known as…

Answer 23

a sigma bonding molecular orbital

Question 24

A pi bond is also known as…

Answer 24

a pi bonding molecular orbital

Question 25

‘The number of atomic orbitals combined is equal to the number of molecular orbitals formed’
_ atomic orbitals combine to form a sigma or pi bond, and _ molecular orbitals form (one is ___, one is ___).

Answer 25

2, 2 (one bonding, one antibonding)

Question 26

In a molecule of methane, the four ___ hybrid orbitals overlap __-on with the ___ atomic orbitals of four hydrogen atoms.

Answer 26

sp3, end-on, 1s

Question 27

In a molecule of fluorine, a __ atomic orbital from each atom overlaps __-on to form the ___ bonding molecular orbital.
This demonstrates that ___ does not occur in all atoms, and is not required for sigma bonds.

Answer 27

2s, end, sigma.
hybridisation

Question 28

2p + 2p -> __
atomic + atomic -> molecular

Answer 28

p^2

Question 29

Pi bonds can only exist between…

Answer 29

p orbitals

Question 30

Therefore pi bonds can never form as a result of ____ of orbitals

Answer 30

hybridisation

Question 31

The first bond between two atoms is always a ___ bond and the rest are always ___ bonds.

Answer 31

sigma, pi

Question 32

Pi bonds produce regions of ___ density, above and ___ the axis of the ___.

Answer 32

electron, below, bond

Question 33

Electrons in a bonding molecular orbital stabilise the molecule because…

Answer 33

they are between the nuclei

Question 34

The fact that electrons in bonding molecular orbitals are between the nuclei, means they have…

Answer 34

lower energies

Question 35

Antibonding orbitals place less ___ ___ between the ___.

Answer 35

electron density, nuclei

Question 36

In a non-polar (pure) covalent bond, where is the bonding molecular orbital?

Answer 36

symmetrical about the midpoint of the two atoms (halfway between the two nuclei/atoms)

Question 37

In polar covalent bonds, the (bonding/antibonding) molecular orbitals are…

Answer 37

(bonding), asymmetrical about the midpoint of the two atoms

Question 38

In a polar covalent bond, the atom with the greater ____ has a greater ___ of the ___, and is therefore…

Answer 38

electronegativity, share, electrons, (partially) negatively charged

Question 39

Ionic compounds have extreme ___ of ___ molecular orbitals between atoms.
The bonding molecular orbital is…

Answer 39

asymmetry, bonding.
almost entirely around the atom with stronger electronegativity

Question 40

What results in the formation of ions?

Answer 40

the bonding MO of two atoms being almost completely around one of them, due to the v large difference in electronegativity.