Chapter 5 - Electrons and Bonding

Question 1

Shells are regarded as what?

Answer 1

Energy levels

Question 2

What happens to energy as the shell number increases?

Answer 2

Energy increases

Question 3

What is the shell number referred to as?

Answer 3

Principal quantum number

Question 4

What are shells made up of?

Answer 4

Atomic orbitals

Question 5

How many electrons can be held in an orbital?

Answer 5

One or two, no more.

Question 6

What can an electron be thought of as?

Answer 6

A negative-charge cloud with the shape of the orbital, called an electron cloud.

Question 7

What are the different orbitals?

Answer 7

S-orbitals
P-orbitals
D-orbitals
F-orbitals

Question 8

How many orbitals does each type contain?

Answer 8

S - one
P - three
D - five
F - seven

Question 9

How many electrons can be held in each orbital type?

Answer 9

S - two
P - six
D - ten
F - fourteen

Question 10

What is the shape of an s-orbital?

Answer 10

Spherical

Question 11

What is the shape of a p-orbital?

Answer 11

Dumbbell

Question 12

What are the rules of orbital fillings?

Answer 12

Orbitals fill in order of increasing energy.
Electrons pair with opposite spins.
Orbitals with the same energy are occupied singly first.

Question 13

Explain the rule of orbitals filling in order of increasing energy

Answer 13

1s is filled first.
For n=2 shell, filling order is: 2s, 2p
For n=3 shell, filling order is 3s, 3p, 3d

Question 14

Where does this rule cause confusion?

Answer 14

The 3d sub-shell has higher energy than the 4s.

So the 4s fills before the 3d.

Question 15

Explain the rule of electrons pair with opposite spins

Answer 15

Electrons are negatively charged and repel one another.
Electrons can have spin up or spin down.
If electrons have opposite spin, the charge repulsion is counteracted enough for both to be in the orbital.

Question 16

Explain the rule of orbitals with the same energy are occupied singly first

Answer 16

Within a sub shell, the orbitals have the same energy. One electron occupies each orbital before pairing begins. This prevents repulsion until no unoccupied orbitals remain.

Question 17

How can electron configuration be shortened?

Answer 17

1s2 can be expressed as [He].
1s2 2s2 2p6 can be expressed as [Ne].
1s2 2s2 2p6 3s2 3p6 can be expressed as [Ar].

Question 18

What happens in terms of energy sub-shells when forming ions?

Answer 18

The highest energy sub-shells lose or gain electrons.

Question 19

What is ionic bonding?

Answer 19

The electrostatic attraction between positive and negative ions.

Question 20

What is the result of ions attracting oppositely charged ions in all directions?

Answer 20

Giant ionic lattice

Question 21

How are the melting and boiling points of ionic compounds explained?

Answer 21

High temperatures are required to provide the energy sufficient to overcome the strong electrostatic attraction between the ions.

Question 22

What happens to the melting points for giant ionic lattices, when ionic charge increases?

Answer 22

Melting point increases as there is a stronger attraction between ions.

Question 23

Are ionic compounds soluble?

Answer 23

They dissolve in polar solvents such as water.

Question 24

What does solubility require?

Answer 24

The ionic lattice must be broken down.

Water molecules must attract and surround the ions.

Question 25

What does solubility (of ionic compounds) depend on?

Answer 25

The relative strengths of the attractions within the giant ionic lattice and the attractions between ions and water molecules.

Question 26

When can ionic compounds conduct electricity?

Answer 26

Not in the solid state.

When molten or dissolved in water.

Question 27

Why can’t ionic compounds conduct electricity when solid?

Answer 27

The ions are in a fixed position.

There are no mobile charge carriers.

Question 28

Why can ionic compounds conduct electricity when molten or dissolved in water?

Answer 28

The solid ionic lattice breaks down.

The ions are now free to move as mobile charge carriers.

Question 29

Summarise the properties of most ionic compounds

Answer 29

High melting and boiling points.
Tend to dissolve in polar solvents such as water.
Conduct electricity only in the liquid state or in aqueous solution.

Question 30

What is covalent bonding?

Answer 30

The strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms.

Question 31

What actually is a covalent bond?

Answer 31

The overlap of atomic orbitals, each containing one electron, to give a shared pair of electrons.

Question 32

How does covalent bonding differ to ionic bonding?

Answer 32

The attraction is localised, acting only on the shared pair of electrons and the two nuclei of the bonded atoms.

Question 33

How can covalent bonding be displayed?

Answer 33

With dot and cross diagrams.

Question 34

What is a multiple covalent bond?

Answer 34

Two atoms share more than one pair of electrons.

Question 35

What is a double bond?

Answer 35

The electrostatic attraction is between two shared pairs of electrons, and the nuclei of the bonding atoms.

Question 36

What is a triple bond?

Answer 36

The electrostatic attraction is between three shared pairs of electrons, and the nuclei of the bonding atoms.

Question 37

What is a dative covalent bond?

Answer 37

The shared pair of electrons has been supplied by one of the bonding atoms only. Originally a lone pair.

Question 38

Give an example of a dative covalent bond

Answer 38

An ammonia molecule donates its lone pair of electrons to an H+ ion.
Forming an ammonium ion.

Question 39

What is average bond enthalpy?

Answer 39

A measurement of covalent bond strength.

Larger value = stronger bond