Structures And Bonding

Question 1

What is covalent bonding?

Answer 1

Covalent bonding is when 2 non metal atoms share a pair of electrons to form a covalent bond.

Question 2

What is ionic bonding?

Answer 2

Ionic bonding is when metal and non metals react to form an ionic compound. Non metals lose electrons and metals gain electrons.

Question 3

What is an ion?

Answer 3

Ions are charged particles formed when an atom loses or gains electrons

Question 4

What is an ionic bond?

Answer 4

The electrostatic forces of attraction between two oppositely charged ions

Question 5

What if a double covalent bond?

Answer 5

A double covalent bond is where 2 pairs of electrons are shared between non metal atoms rather then just one. It is represented like this ‘=’

Question 6

What are the properties of simple molecules?

Answer 6

Simple molecules( like carbon dioxide and methane) only contain a few atoms held together by strong covalent bonds.
They have weak intermolecular forces which are easy to overcome without much energy( meaning they have low melting and boiling points)
They are non conductive because they do not have free electrons which can move and carry a charge

Question 7

How do the industrial conditions of polythene affect the type that is made?

Answer 7

High density Polythene: low temperatures(60 degrees), few atmospheres pressures but it requires a catalyst.
Low density: high temperatures( 200 degrees) and high atmospheres pressures

Question 8

Why are shape memory alloys?

Answer 8

Alloys that return to their original shape on heating after being deformed. For example Nitinol in dental braces

Question 9

What are thermosoftening polymers?

Answer 9

Polymers which soften when heated and can be shaped when hot.

Question 10

What are the structures of thermosoftening polymers?

Answer 10

Weak intermolecular forces between tangled polymer chains( which can be overcome without much energy)
Chains have no cross links so can slide over each other easily.

Question 11

What are thermosetting polymers?

Answer 11

Polymers that once moulded do not soften with heat and they can’t be reshaped. An example is vulcanised rubber.

Question 12

What are the structure of thermosetting polymers?

Answer 12

Its polymer chains are joined together by cross links, these are very strong so they cannot slide over each other easily.
Chains with strong intermolecular( so a lot of energy is needed to overcome them)

Question 13

What are alloys?

Answer 13

Alloys are a mixture of metals.

Question 14

What are properties of metals?

Answer 14

Most have high melting points Malleable
Good conductors of heat and electricity
Strong

Question 15

What is metallic bonding?

Answer 15

Metallic bonding is the electrostatic attraction between delocalised electrons and positive metal ions.

There are strong electrostatic forces of attraction between the negatively charged electrons and positive metal ions which bond the metal ions together to form the ‘metallic bond’

These are very strong and need a lot of energy to overcome

Question 16

Why are metals malleable?(be bent into shape)

Answer 16

The delocalised electrons allow metals to distort, when struck the regular layer of metal atoms can slide over each other easily, without breaking up the structure of the metal.

Question 17

What are metals good conductors of electricity?

Answer 17

Has free electrons which can move around the structure of the metal and carry a charge

Question 18

What is nanoscience?

Answer 18

It refers to the science of structures between 1-100Nm Nano meters are defined as one billionth of a meter.

Question 19

What are the properties and uses of nanoscience?

Answer 19

Nano particles have a very large surface area to volume ratio so they are often able to react quickly, making them useful catalysts.

They are used in sun screen( this is because they are so small they do not reflect visible light, so they block harmful UV rays without appearing white on skin)

Cosmetics such as perfume

Question 20

What is the structure and bonding in diamond?

Answer 20

Diamond contains a lot of non metal atoms( carbon) all in a giant covalent structure. These are held by strong covalent bonds
Each carbon atom forms 4 very strong covalent bonds.
These are very hard to break and need lots of energy to be overcome , so diamond is very hard
It does not conduct electricity though as there are no free electrons.

Question 21

Why is graphite soft?

Answer 21

Graphite is another giant covalent structure

In graphite each carbon atom bonds to 3 others, forming layers. Graphite is soft because there are no covalent bonds between the LAYERS .
Furthermore there are weak intermolecular forces between the layers in graphite.
These are overcome easily without much energy needed.
All of this enables the layers in graphite to slide over each other easily.

Question 22

Why can graphite conduct electricity?

Answer 22

4 electrons on outer shell for bonding, since each carbon atom forms 3 strong covalent bonds there is a spare outer electron on each carbon atom This can move around the layers of graphite and conduct electricity.

Question 23

What are the properties of ionic compounds and why?

Answer 23

Conduct electricity when molten or dissolved( ions are free to move around and carry a current, as water molecules separate the ion from the lattice structure and high temperatures provide enough energy to overcome the many attractive forces between the ions)

High melting point( strong ionic bonds which require lots of energy to overcome).

Question 24

What are fullerenes and what are they used for?

Answer 24

Carbon atoms joined together to form large cages. They are built up of hexagonal rings of carbon.

Fullerenes are used in the delivery of drugs to specific parts of the body.

Question 25

Why are alloys harder than pure metals?

Answer 25

Different sized atoms
Distort regular arrangement
Harder for atoms to slide over each other

Question 26

What are the problems with nano particles?

Answer 26

The effects on human health have not been fully investigated properly
We are not aware of the long term effects of this fairly new technology.
So more research us required

Question 27

Why do metals form crystals?

Answer 27

Because the atoms are built up layer upon layer in a regular structure

Question 28

Why are electrodes replaced?

Answer 28

Wear away as it produces carbon dioxide( carbon electrodes react with oxygen).