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 are the different orbitals?

Answer 6

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

Question 7

How many orbitals does each type contain?

Answer 7

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

Question 8

How many electrons can be held in each orbital type?

Answer 8

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

Question 9

What is the shape of an s-orbital?

Answer 9

Spherical

Question 10

What is the shape of a p-orbital?

Answer 10

Dumbbell

Question 11

What are the rules of orbital fillings?

Answer 11

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

Question 12

Where does this rule cause confusion?

Answer 12

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

So the 4s fills before the 3d.

Question 13

Explain the rule of electrons pair with opposite spins

Answer 13

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 14

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

Answer 14

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 15

How can electron configuration be shortened?

Answer 15

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 16

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

Answer 16

The highest energy sub-shells lose or gain electrons.

Question 17

What is ionic bonding?

Answer 17

The electrostatic attraction between positive and negative ions.

Question 18

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

Answer 18

Giant ionic lattice

Question 19

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

Answer 19

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

Question 20

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

Answer 20

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

Question 21

Are ionic compounds soluble?

Answer 21

some ionic compounds are soluble and they dissolve in polar solvents such as water. The ones that do not: have larges charges so hard for the polar water molecules to break down the lattice and surround each ion in solution.

Question 22

What does solubility require?

Answer 22

The ionic lattice must be broken down.

Water molecules must attract and surround the ions.

Question 23

What does solubility (of ionic compounds) depend on?

Answer 23

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

Question 24

When can ionic compounds conduct electricity?

Answer 24

Not in the solid state.

When molten or dissolved in water.

Question 25

Why can’t ionic compounds conduct electricity when solid?

Answer 25

The ions are in a fixed position.

There are no mobile charge carriers.

Question 26

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

Answer 26

The solid ionic lattice breaks down.

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

Question 27

Summarise the properties of most ionic compounds

Answer 27

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 28

What is covalent bonding?

Answer 28

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

Question 29

What actually is a covalent bond in terms of atomic orbital?

Answer 29

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

Question 30

How does covalent bonding differ to ionic bonding?

Answer 30

For covalent bonding the attraction is localised; attraction acting only on the shared pair of electrons and the nuclei of the bonding atoms.

ionic, however; attracts in all directions in three dimesions.

Question 31

How can covalent bonding be displayed?

Answer 31

With dot and cross diagrams.

Question 32

What is a multiple covalent bond?

Answer 32

Two atoms share more than one pair of electrons.

Question 33

What is a double bond?

Answer 33

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

Question 34

What is a triple bond?

Answer 34

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

Question 35

What is a dative covalent bond?

Answer 35

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

Question 36

Give an example of a dative covalent bond

Answer 36

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

Question 37

What is average bond enthalpy?

Answer 37

A measurement of covalent bond strength.

Larger value = stronger bond

Question 38

She’ll formula =

Answer 38

2n^2

Question 39

At what stage do atoms not follow the octet rule

Answer 39

n=3, when a d-subshell becomes available for the expansion.

This is called the expansion of the octet