Chemical bonding 01

Question 1

ionic bonds

Answer 1

Positive and negative ions are held strongly together by electrostatic forces of attraction in a giant lattice structure

Question 2

Cation

Answer 2

Generally, metals form positive ions

Question 3

Anion

Answer 3

Generally, non-metals form negative ions

Question 4

Arrangment of ions in ionic bond NaCl

Answer 4

[Na][Cl] [Na][Cl]
[Cl] [Na][Cl] [Na]
[Na][Cl] [Na][Cl]
Na+ & Cl- are each surrounded by oppositely charged ions attracted by strong electrostatic forces of attraction in a regular lattice

Question 5

ionic Propety - High boiling points and melting points

Answer 5

strong electrostatic forces of attraction between positive and negative ions requires a lot of energy to break them apart

Question 6

ionic Property - they’re hard but brittle

Answer 6

+ - + - + -
- + - + - +
+ - + - + -
- + - + - +

A force makes the layer slide
+ - + - + -
- + - + - +
+ - + - + -
- + - + - +

There is repulsion between ions with the same charge
+ - + - + -
- + - + - +

    \+ - + - + -
    - + - + - +

Question 7

ionic property - They are generally soluble in water

Answer 7

ions are attracted to the polar water molecules and the attraction breaks lattice apart

Question 8

ionic property - they cannot conduct electricity in the solid-state

Answer 8

as solids ionic compounds cannot conduct electricity because the ions are bonded together in a lattice

Question 9

ionic property - they can conduct electricity as liquid’s i.e. when molten or dissolved in water.

Answer 9

When liquid/molten or dissolved in water the ions are free to move so electricity can be conducted

Question 10

Covalent bonding

Answer 10

between two or more non-metal elements

Question 11

Covalent bonds

Answer 11

• Consists of a shared pair of electrons
• sometimes called molecular bonds
• Two types of covalent substances simple covalent and giant covalent

Question 12

Formation of covalent bonds

Answer 12

each atom donates one electron to the shared pair of electrons making up the covalent bond. By doing this each atom has a full outer shell of electrons due to the shared Electrons.

Question 13

Double or triple covalent bonds

Answer 13

sometimes atoms can share two or three electron pairs to form double and triple covalent bonds.

Question 14

Strength of simple covalent substances

Answer 14

• the covalent bonds between the atoms in a molecule are strong
• the forces between neighbouring molecules are weak i.e. intermolecular forces

Question 15

simple covalent properties: Low melting and boiling points

Answer 15

weak into molecular forces of attraction which require less energy to be broken resulting in low melting and boiling point.

Question 16

simple covalent properties: Electrical conductivity is poor

Answer 16

no ions of free electrons are present

Question 17

simple covalent properties: solubility in water

Answer 17

poor - no charged particles present to be attracted to the polar water molecules.

Question 18

Giant covalent substances of the element carbon

Answer 18

diamond and graphite

Question 19

Diamond structure

Answer 19

each carbon atom is joined to 4 others by strong covalent bond

Question 20

Graphite structure

Answer 20

• each carbon atom is joined to three others within a layer
• Strong covalent bonds throughout the layer
• weak intermolecular forces between layers

Question 21

Melting point of diamond

Answer 21

very high due to a lot of very strong covalent bonds needing to be broken

Question 22

melting point of graphite

Answer 22

very high due to a lot of very strong covalent bonds needing to be broken

Question 23

Diamond hardness

Answer 23

very hard due to very strong covalent bonds throughout the structure

Question 24

graphite hardness

Answer 24

soft due to weak intermolecular forces between layers - layers can slide

Question 25

electrical conductivity of diamond

Answer 25

no - all outer electrons are in covalent bonds - no delocalised electrons

Question 26

electrical conductivity of graphite

Answer 26

very good - has delocalised electrons in between layers that can move freely

Question 27

Diamond industrial use

Answer 27

• Drill gits due to hardness
• jewellery do to shininess

Question 28

graphite industrial use

Answer 28

• pencil ‘lead’ and lubrication due to Layers ability to slide
• used as electrodes due to good electrical conduction

Question 29

Metallic bonding

Answer 29

bonding which holds metals together

Question 30

Metallic structure

Answer 30

in a metallic structure positive metal ions (consisting of the nucleus and inner shell electrons) all held together by outer shell electrons which become delocalised i.e. Not attached to one particular atom, but with certain freedom to move.

Question 31

Metallic properties: high melting and boiling points

Answer 31

lots of energy required to break the attractive forces between delocalised electrons and positive ions

Question 32

Metallic properties: are malleable and ductile

Answer 32

layers of ions can move and slide or be pulled into a wire

Question 33

Metallic properties: good conductors of electricity

Answer 33

many delocalised electrons present - electrons which are free to move

Question 34

Metallic properties: good conductors of heat

Answer 34

delocalised electrons gain kinetic energy when heated and transfer faster through the metal gaining heat

Question 35

Why are alloys tougher than pure metals

Answer 35

layers will struggle to slide

Question 36

graphene

Answer 36

Graphene is a sheet of carbon atoms joined together in hexagons - its basically a single layer of graphite. It is light and very strong (due to the strong covalent bonds in a layer) so is added to materials to improve strength without adding much weight. It can also conduct electricity as it has delocalised electrons like graphite.

Question 37

Polymers

Answer 37

Polymers eg polethene are long chains of covalently bonded carbon atoms (1000s of atoms long). They are usually solid at room temperature as the intermolecular forces are stronger due to the size of the molecule. They are often flexible as the polymer chains can slide over each other so can be used to make plastic bags or plastic wrapping.

Question 38

ceramics

Answer 38

Question 39

polymers

Answer 39

Question 40

composite materials

Answer 40

Question 41

glass

Answer 41

Question 42

metal

Answer 42

Question 43

nanoparticles

Answer 43

Nanoparticles are 1-100 nanometers across.
They contain a few hundred atoms.
Nanoparticles include fullerenes, cage like structures of carbon. C60 is called Buckminster fullerene and it is a football shaped molecule.
A nanoparticle has different properties to the ‘bulk’ chemical it’s made from due to its high surface area to volume ratio. e.g fullerenes have different properties to graphite and diamond, gold nanoparticles look red not gold.

Question 44

uses of nanoscience

Answer 44

They have a high surface area to volume ratio, and therefore would make good catalysts.
They can also be used to produce highly selective sensors.
e Nanotubes could make stronger, lighter building materials.
New cosmetics, e.g sun tan cream and deodorant. Suncreams that contain nanoparticles are colourless and leave no white marks on the skin.
Lubricant coatings, as they reduce friction. These can be used for artificial joints and gears. Nanotubes conduct electricity, so can be used in small electrical circuits for computers.

Question 45

risks of nanoparticles

Answer 45

They are new materials and they have not undergone long term testing to see if they impact human health or the environment over the timespan of decades.
Their small size means they can be easily absorbed through the skin.

Question 46

Ionic bonding

Answer 46

between metals and non-metals