Bonding

Question 1

What do these state symbols mean? (l) (g) (aq)

Answer 1

liquid, gas, aqueous

Question 2

What are electrostatic forces like in ionic compounds?

Answer 2

Strong electrostatic forces of attraction in all directions between oppositely charged ions

Question 3

Melting point and boiling points in ionic compounds?

Answer 3

High because large amounts of energy are needed to break the many strong bonds

Question 4

What happens to ionic compounds when melted or dissolved in water?

Answer 4

They conduct electricity bc ions are free to move and so charge can flow

Question 5

What are the intermolecular forces like between small molecules?

Answer 5

Weak

Question 6

What happens when substance melts or boils?

Answer 6

Intermolecular forces are overcome.

Question 7

Why do larger molecules have higher melting and boiling points?

Answer 7

Intermolecular forces increase with size of molecules - larger molecules have higher m and b points

Question 8

What are polymers?

Answer 8

Made by chemical reactions that join lots of smaller molecules together into longer ones.

Question 9

Properties of polymers?

Answer 9

Chemically unreactive, solids at room temp, plastic and can be moulded into shape, electrical insulators, strong and hard.

Question 10

What are the bonds like in polymers?

Answer 10

Strong covalent bonds. Intermolecular forces are relatively strong - which is why they are solids at room temp.

Question 11

What are giant covalent structures?

Answer 11

Contain very many atoms, each joined to adjacent atoms by covalent bonds. Usually arranged into giant lattices which are extremely strong structures.

Question 12

Examples of giant covalent structures?

Answer 12

Diamond (forms of carbon) and silicon dioxide (silica)

Question 13

What happens when boiling or melting giant covalent structures?

Answer 13

The strong covalent bonds need to be overcome/broken.

Question 14

Structures of metals?

Answer 14

Giant structures of atoms arranged in a regular pattern. Electrons on outer shell are delocalised and are free to move which results in strong metallic bonding.

Question 15

Why are metals good conductors?

Answer 15

Delocalised electrons - these carry electrical charge through the metal.

Question 16

Properties of metals?

Answer 16

• electrical conductors bc of delocalised electrons that carry electrical charge
• good conductors bc of deloclalised electrons that transfer thermal energy.
• high melting and low boiling points because metallic bonding in giant structure of a metal is very strong. Large amounts of energy are needed to overcome these.

Question 17

What is an alloy?

Answer 17

A mixture of two or more elements where at least one is a metal.

Question 18

Property of alloys? And its relationship to metals?

Answer 18

Hardness - sometimes pure metals are too soft for many uses. these can be made harder by adding another element to it, forming an alloy, and increasing hardness.

e.g pure iron is very soft. adding tungsten makes tool steel, which is harder. steels are examples of alloys.

Question 19

Why are alloys hard?

Answer 19

In atom structures, atoms slide over each other when a force is applied. Greater the force needed = harder and stronger metal.

In an alloy, there are atoms of different sizes. The smaller or bigger atoms distort the layers of atoms, which means a greater force is required for layers to slide over each other. Alloy is harder and stronger than the pure metal.

Question 20

Structure and bonding of diamond?

Answer 20

Each carbon atom is joined together to four other carbon atoms by strong covalent bonds.
The carbon atoms form a tetrahedral structure
There are no free electrons

Question 21

Properties and uses of diamond?

Answer 21

The rigid structure and strong covalent bonds makes diamond very hard. Makes it useful for cutting tools eg oil rig drills.
Has a very high melting point and does not conduct electricity.

Question 22

Structure and bonding of graphite?

Answer 22

• A giant covalent structure with each carbon atom forming three covalent bonds with other carbon atoms
• Carbon atoms form layers of hexagonal rings
• No covalent bonds between layers
• One delocalised electron from each atom

Question 23

Properties of graphite and their uses?

Answer 23

• Graphite had delocalised electrons which carry electrical charge. Makes graphite useful for electrodes in batteries and for electrolysis.
• Forces between layers are weak, which means they can slide over one another. Makes graphite slippery so it is useful as a lubricant.

Question 24

What are nano particles?

Answer 24

Structures that are between 1 and 100 nm in size. Made up a few hundred of atoms.

Question 25

What are nano particles measured in?

Answer 25

Nm (nanometres)

Question 26

Two properties of nano particles and their uses?

Answer 26

Small size - they can penetrate into body which could be useful for medicinal research, can be mixed with other materials to form composite materials, used in some paints, sunscreens. Nanoparticles of silver are added into a special type of sock, which kill bacteria that cause smelly feet.

High surface area to volume ratio - make excellent catalysts. Self cleaning window panes have nano particle coatings - when light hits it, they break down dirt.

Question 27

What are the three types of bonding?

Answer 27

Ionic, metallic, covalent.

Question 28

What is ionic bonding?

Answer 28

Occurs in compounds that contain a metal and a non metal. They bond to form metal compounds.

Question 29

What is covalent bonding?

Answer 29

Between two non metal atoms. Occurs when two atoms share electrons to obtain a stable outer shell.

Question 30

What is metallic bonding?

Answer 30

Between metals. Its the attraction between the positive ions in a regular lattice and its delocalised electrons.