Ionic, Covalent, Metallic Bonding

C4.1.1 Intro and PKR: Metals C4.1.2 Ionic Bonding C4.1.3 Properties of Ionic Substances C4.1.4 Covalent Bonding C4.1.5 Properties of Covalent Substances C4.1.6 Diamond C4.1.7 Graphite C4.1.8 Graphene, Fullerenes and Nanotubes,,,,, \metallic bonding do nanotubes & nanoparticles

Atoms are very small and have a radius of about…

1x10^-10m.

State the definition of an element

A pure substance made up of only one type of atom.

Atomic Number

The number of protons in an atom

Mass Number

The number of protons and neutrons in the nucleus of an atom

What did Niels Bohr do?

• developed the Bohr model of the atom: electrons orbit the nucleus in the energy levels

ions

Atoms that have gained or lost electrons

What type of elements form negative ions?

Non-metals

What type of elements form positive ions?

Metals

Explain why atoms are considered electrically neutral.

Atoms have equal numbers of protons, which are positively charged and electrons, which are negatively charged. This means that the charges cancel each other out.

Explain what it means for an atom to be stable.

It has a full outer shell.

Where does ionic bonding occur?

in compounds formed from metals combined with non-metals.

Describe

• The sodium atom transfers an electron to the fluorine atom

• This forms a sodium ion and a fluoride ion

• These oppositely charged ions have a strong electrostatic force of attraction called ionic bonding

valence electrons

electrons in outer shell

• Each sodium loses 1 electron

• Oxygen needs 2 electrons for a stable configuration

• Oxygen gains 1 electron from each sodium

• It forms the ionic compound Na₂O, sodium oxide.

What is sodium oxide used for?

ceramics and eye glasses.

What hazards are associated with sodium oxide?

Sodium oxide is corrosive, and it reacts violently with water.

Properties of ionic substances

• They conduct electricity when molten or in solution.

• They are hard solids,

• They have high melting and boiling points.

• They have crystalline structures

The structure of ionic substances

• have a giant lattice structure, also called an ionic lattice

• have a regular, repeating pattern of oppositely charged ions

• are held together by strong electrostatic forces of attraction (also called ionic bonds)

Why do ionic substances have high melting and boiling points?

due to strong electrostatic forces of attraction between oppositely charged ions. These require large amounts of energy to overcome.

Why can’t ionic substances conduct electricity as solids?

their ions are held in a fixed, rigid crystal lattice and are not free to move

Why can ionic substances conduct electricity when molten or dissolved in solution?

because the ions are free to move and carry the charge

Why can ionic substances form hard, crystalline structures

because the ions are tightly packed in a regular, repeating structure called an ionic lattice

What is ethanol used for?

the manufacture of plastics, fertilisers, alcoholic drinks and cosmetics.

What are ionic bonds caused by?

the electrostatic forces of attraction between oppositely charged ions.

compound

two or more elements combined together chemically.

Covalent bonding

where two or more non-metal atoms share pairs of electrons in order to achieve a stable electronic configuration

How is a single covalent bond represented?

A single covalent bond is represented by a single line, for e.g. H-H

How is a double covalent bond represented?

A double covalent bond is represented by a double line, for e.g. O=O

How is a triple covalent bond represented?

A triple covalent bond is represented by a triple line, for e.g. N≡N

What is a double covalent bond?

A double covalent bond is 2 shared pairs of electrons

What is the formula for methane?

The formula for methane is CH₄

percentage by mass equation

% by mass = mass of element 

                     ————————      x100

                     mass of compound

concentration equation

concentration = mass divided by volume

Properties of simple covalent substances & explanations

• low melting and boiling points - are liquid or gas at room temperature: they have weak intermolecular forces of attraction between the molecules. These require little energy to overcome and melt or boil the substance.

• cannot conduct electricity: because the molecules are neutral (no charge), they do not have any free electrons or ions to carry a charge.

Properties of giant covalent substances

• high melting and boiling points

• are solid at room temperature

• may conduct electricity

intermolecular forces

the forces that exist in between molecules

examples of simple covalent substances

• water

• methane

• carbon dioxide

examples of giant covalent substances

• diamond

• graphite

• graphene

As molecules increase in size, the intermolecular forces get…

bigger

Are covalent bonds weak or strong?

Strong

Describe the physical appearance of chlorine.

Chlorine is a green-yellow gas.

What type of bonding is present in chlorine gas?

Covalent bonding

appearance & smell of methane

colourless & odourless

diatomic molecule

a molecule made of two atoms

What word describes a substance that dissolves?

Soluble

What word describes a substance in which other substances are dissolved in?

Solvent

Write down the formula to calculate pressure.

Pressure = force ÷ area

What is diamond used for and why?

It is used for making jewellery, and for the tips of cutting tools like drills and saws, because it is a very hard and valuable substance.

The structure of diamond

1. Each carbon atom is joined to 4 other carbon atoms by covalent bonds ..so diamond has a high melting point ..because it takes lots of energy to overcome all of these strong covalent bonds

2. Many, many carbon atoms are joined up to create a giant lattice arrangement which is held together by strong covalent bonds. ..which means that diamond is a hard substance ..because the rigid network of carbon atoms, held together by strong covalent bonds, takes a lot of energy to break.

3. There are no delocalised (free) electrons ..which means that diamond does not conduct electricity ..because there are no delocalised electrons to carry an electrical charge

Properties & uses of graphite

• Graphite is a giant covalent substance.

• Graphite is a soft substance.

It is used

• in pencils, because it’s soft, and layers of graphite slide off as you rub it against a page, because the carbon atoms in graphite are arranged in layers, with only weak forces holding those layers together.

• as a lubricant in machinery because it’s soft and slippery, and layers of graphite slide off easily, because the carbon atoms in graphite are arranged in layers, with only weak forces holding those layers together.

• to make electrodes because graphite conducts electricity, because it contains delocalised electrons that carry charge through the structure.

The structure of graphite

• Each carbon atom is bonded to 3 other carbon atoms by strong covalent bonds: There is one delocalised electron for every carbon atom.

• The carbon atoms are arranged in layers; these layers are held together by weak intermolecular forces. This means that each layer can slide off easily.

Allotropy

a property shown by some elements that can exist in different forms, e.g. allotropes of carbon include diamond, graphite, graphene, fullerene, and carbon nanotubes

Compare the structure of diamond and graphite.

• Both diamond and graphite are giant covalent structures made of carbon atoms

• Both diamond and graphite contain strong covalent bonds.

• In diamond, a rigid network of carbon atoms is held together by strong covalent bonds, whereas in graphite, the carbon atoms are arranged in layers, with only weak intermolecular forces holding these layers together.

• In diamond each carbon atom makes 4 bonds with other carbon atoms, whereas in graphite, each carbon atom only makes 3 bonds with other atoms

The structure of graphene

1. Graphene is made of carbon atoms

2. Each carbon atom is bonded to 3 other carbon atoms by strong covalent bonds

3. There is one delocalised electron for every carbon atom

Uses of graphene & why

• Graphene is used in construction materials because graphene is strong because it is a giant lattice structure containing many strong covalent bonds which require a lot of energy to be broken.

• Graphene is used in electronics because graphene conducts electricity because it contains delocalised electrons that carry charge through the structure.

How many atoms thick is graphene?

The graphene is 1 atom thick.

Fullerenes

Fullerenes are molecules of carbon atoms with hollow shapes.

• Each structure is made up of hexagonal rings of carbon atoms.

• The first fullerene to be discovered was buckminsterfullerene.

• Buckminsterfullerene has the formula C₆₀.

What type of bonding is there

1. between the atoms that make up the molecule

2. in between molecules of fullerene?

1. Strong covalent bonds

2. Weak intermolecular forces

Carbon Nanotubes

examples of fullerenes: they have a cylindrical shape, with a high length to diameter ratio.

structure of carbon nanotubes (just like graphene) & properties as a result

• carbon nanotubes are made of carbon atoms

• there are strong covalent bonds between the carbon atoms: have a high tensile strength

• each carbon atom has a delocalised electron: conduct electricity

• are slippery (high length to diameter ratio)

Who discovered the electron? 

J.J. Thompson

What is a silver alloy?

a mixture of silver and another element.

What are some properties of pure silver?

Pure silver is very soft and reacts with air

Metallic bonding

the force of attraction between the positive metal ions and the ‘sea’ of delocalised electrons forming a giant metallic structure

Why do most metals have high melting and boiling points?

strong metallic bonds

alloy

a mixture of chemical elements where at least one is a metal

Alloys uses

such as in construction and for dental braces

Shape memory alloys uses

for spectacles

Shape Memory Alloys transformation process

Pure metals are … and … than alloys

softer and weaker

The structure of metals

• Metals have a giant structure

• Particles are in a regular arrangement

• Particles are arranged in layers, which can slide over each other, allowing metals to be bent and shaped easily

The structure of alloys

• Alloys have a giant structure

• Particles are in an irregular arrangement because atoms are different sizes

Particles are not arranged in layers, so alloys cannot easily be bent and shaped

Which material would be a better electrical conductor, pure copper or a copper alloy?

Pure copper. This is because it is easy for electrons to flow through the regular layers carrying a charge. 

In the alloy, the layers are disrupted/distorted. This makes it harder for the electrons to flow through the material.