Chapter 5

Question 1

What are the shells regarded as?

Answer 1

Energy levels, which are called the principal quantum number, n.

Question 2

How can electrons move between energy levels?

Answer 2

They move by absorbing or emitting energy equal to the difference in energy between two energy levels.

Question 3

What is an atomic orbital?

Answer 3

A region around the nucleus which can hold up to 2 electrons with opposite spins. It is also a region of space where there is a high proportion of finding an electron with a certain quanta of energy.

Question 4

What are s- orbitals?

Answer 4

The electron cloud, is a sphere shape, with each shell from n=1 upwards containing 1 s-orbital. The greater the shell numbers the greater the radius of its s-orbital.

Question 5

What are p- orbitals?

Answer 5

They have an electron cloud shaped like a dumbbell, which have 3 separate orbitals all at right angles of one another. Each shell from n=2 has 3 p-orbitals. The greater the shell number the further the p orbital is from the nucleus.

Question 6

What are d-orbitals and f-orbitals?

Answer 6

Each shell from n= 3 contains 5 d- orbitals

Each shell from n=4 contains 7 f-orbitals

Question 7

How many electrons are there in each shell?

Answer 7

n=1 –> 2
n=2 –> 8
n=3 –> 18
n=4 –> 32

Question 8

What are sub shells?

Answer 8

Within a shell, orbitals of the same type are grouped into sub shells. Each shell gains a new type of orbital, the number of orbitals increase with the each new orbital type. Two electrons can fit in each orbital, so the number of electrons in a sub shell also increases.

Question 9

How do the orbitals fill?

Answer 9

They fill in order of increasing energy, the new type of shell added to each shell has a higher energy level.

Question 10

Tell me the order of how the orbitals fill?

Answer 10

n=2 2s, 2p
n=3 3s,3p,3d
n=4 4s,4p,4d,4f

Question 11

Where is there an overlap with orbitals?

Answer 11

The highest energy level on n=3 overlaps with the lowest level of n=4. The 3d has a higher energy level than the 4s, so the 4s fills before the 3d. So the order goes 3p,4s,3d

Question 12

Describe electron pairs with opposite spins?

Answer 12

Each orbital can hold 2 electrons with opposite spins. As electrons are negatively charged they repel each other. They spin, either up or down. An electron can be shown as an arrow indicating its spin. Two electrons in a orbital must have opposite spins to covert the repulsion between the negative charges.

Question 13

How does the electrons pair?

Answer 13

One electron has to occupy each orbital before pairing can start, this prevents any repulsion between the paired electrons until there is no further orbital available at the same energy level.

Question 14

What happens when ions form?

Answer 14

The highest energy levels lose or gain electrons

Question 15

What happens with the 4s sub shell when electrons are gained and lost?

Answer 15

It fills before 3d and empties before 3d.

Question 16

What is ionic bonding?

Answer 16

It is the electrostatic attraction between positive and negative ions. It holds cations and anions in ionic compounds.

Question 17

How are ionic compounds indicated?

Answer 17

Using a dot and cross diagram., with only the outer electrons being represented, with the electrons being transferred from the metal to the non metal. The diagram should be separate with brackets around them, with their ionic charge shown in the upper right hand corner.

Question 18

Describe the structure of ionic compounds?

Answer 18

Each ion attracts oppositely charged ions very strongly, in all directions. This results in a giant ionic lattice which contains billions of ions, this structure occurs at solid state. Ions are packed closely together in a regular lattice arrangement.

Question 19

Do ionic compounds have high or low melting points?

Answer 19

Almost all are solid at room temperature, as there is insufficient amount of energy to overcome the electrostatic forces between the opposite charged ions in a giant ionic lattice. High temperatures are required to overcome the electrostatic attraction between the ions. Therefore most ionic compounds have a high melting and boiling point.

Question 20

Describe the solubility of ionic compounds?

Answer 20

Many ionic compounds dissolve in polar solvents. Polar water molecules break down the lattice and surrounds each ion in the solution. If a compound has a large ionic charge the attraction maybe too strong for water to break down the lattice, so the compound won’t be very soluble.

Question 21

What does solubility depend on?

Answer 21

The relative strengths of attraction within the lattice and attractions between the ions and water. Solubility decreases as the ionic charges increase

Question 22

What are the two processes which solubility of ionic compounds require?

Answer 22

The ionic lattice must be broken down

Water molecules must attract the surrounding ions

Question 23

What is the electrical conductivity of ionic compounds?

Answer 23

In a solid state, the ionic compound can’t conduct electricity unless it is dissolved or melted. In the solid state, the ions are fixed into position in the giant lattice structure, where there are no mobile charge carriers. However in a aqueous or melted state, the solid ionic lattice breaks down and the ions are free to move as mobile charge carriers, so can now conduct electricity

Question 24

What is covalent bonding?

Answer 24

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

Question 25

Where does covalent bonding occur?

Answer 25

It happens in non metals, compounds of non metallic elements and polyatomic ions.

Question 26

What is a covalent bond?

Answer 26

It is the overlap of atomic orbitals each containing one electron to give a shared pair of electrons. The shared pair is shared to the nuclei of both bonding atoms. The bonded atoms often have outer shells with the same electron structure as their nearest noble gas.

Question 27

How is a covalent bond’s attraction described?

Answer 27

It is localised acting solely between the shared pair of electrons and the nuclei of the bonded atom, which results in a small unit called a molecule consisting of two or more atoms.

Question 28

What is a molecule?

Answer 28

It is the smallest part of a covalent compound that can exist whilst retaining the chemical properties of the compound.

Question 29

How is covalent bonding shown?

Answer 29

By a dot and cross diagram, which shows the electrons being shared between the atoms

Question 30

What is an unpaired electron called?

Answer 30

A lone pair

Question 31

Why does boron differ from the normal rule of covalent bonding?

Answer 31

It only has 3 outer shell electrons, which can be paired. E.g BF3 has three outer shell electrons which are paired, so only has 6 electrons around the boron atom.

Question 32

In SF2 how many unpaired electrons are there?

Answer 32

2 so 2 bonds are possible

Question 33

In SF4 how many unpaired electrons are there?

Answer 33

4 so 4 bonds are possible

Question 34

In SF6 how many unpaired electrons are there?

Answer 34

6 so 6 bonds are possible

Question 35

What is the bonding like in SF6?

Answer 35

The 6 unpaired electrons from sulphur are paired. The outer shell now contains 12 electrons 4 more than argon. This is known as the expansion of an octet and is only possible from n=3 when a d sub shell is present

Question 36

What is a double covalent bond?

Answer 36

In a double bond the electrostatic attraction is between the two shared pairs of electrons and the nuclei of the bonding atoms

Question 37

What is a triple covalent bond?

Answer 37

The electrostatic attraction is between the shared pair of electrons and the nuclei of the bonding atoms.

Question 38

What is a dative covalent bond?

Answer 38

It is a covalent bond in which the shared pair of electrons has been supplied by one of the bonded atoms only. The shared pair of electrons was originally a lone pair on one of the bonded atoms. The dative covalent bond is expressed by an arrow pointing away from the atom which contributed both electrons.

Question 39

Give an example of a dative covalent bond?

Answer 39

An ammonia molecule donates its lone pair of electrons to a H+ ion. The dative covalent bond in NH4+ is shown by a bond with an arrow head to show that the nitrogen has provided both electrons to the covalent bond.

Question 40

Give the number of covalent bonds in the common elements?

Answer 40

Hydrogen - 1
Oxygen - 2
Nitrogen - 3
Carbon- 4