FULL TOPIC 2: BONDING, STRUCTURE, AND PROPERTIES OF MATTER

How are ions made?

When electrons are transferred, atoms gain or lose electrons

What are ions?

Charged particles - they can be single atoms or groups of atoms

What are atoms trying to do when they form ions?

They're trying to get a full outer shell to be stable

What happens when metals form ions?

They lose electrons from their outer shell to form positive ions

What happens when non metals form ions?

They gain electrons into their outer shell to form negative ions

What groups are most likely to form ions?

Groups 1 & 2 and 6 & 7

What are Groups 1 & 2?

Metals and they lose electrons to form positive ions (cations)

What are Groups 6 & 7?

Non - metals and they gain electrons to form negative ions (anions)

What structure do ionic compounds have?

Giant ionic lattice

What do the ions form?

A closely packed regular lattice arrangement with very strong electrostatic forces of attraction between oppositely charged ions, in all directions in the lattice.

What properties do ionic compounds have?

• High melting / boiling points (due to many strong bonds between the ions, takes lots of energy to overcome this)

• Solid = ions held in place , Melted = ions move freely (carry electric charge)

• Some ionic compounds also dissolve in water, the ions separate and are all free to move in the solution, so they'll carry electric charge

How to find the empirical formula in a dot and cross diagram?

Count up how many atoms there are of each element

How to find the empirical formula in a 3D diagram of the ionic lattice?

Use it to work out what ions are in the ionic compound

What is Covalent bonding?

Sharing of electrons

What elements react in covalent bonding?

Non - metals and non - metals

What makes covalent bonds very strong?

The positively charged nuclei of the bonded atoms are attracted to the shared pair of electrons by electrostatic forces

Why do atoms only share electrons in their outer shells?

They have the highest energy levels

Why do non - metals want a full outer shell via covalent bonds?

Electronic structure of a noble gas, which is very stable

How do you show covalent bonds?

Dot and cross diagrams

What is the displayed formula?

Shows the covalent bonds as single lines between atoms, this is showing how connected in large molecules

What are simple molecular substances?

Made up of molecules containing a few atoms joined together by covalent bonds

What are some common examples of simple molecular substances?

Hydrogen, chlorine, oxygen, nitrogen, methane, water, hydrogen chloride

Hydrogen, H2

Hydrogen atoms have just one electron. They only need one more to complete the first shell so they often form single covalent bonds, either with other hydrogen atoms or with other elements to achieve this

Chlorine, Cl2

Each chlorine atom needs just one more electron to complete the outer shell so two chlorine atoms can share one pair of electrons and form a single covalent bond.

Oxygen, O2

Each oxygen atoms needs two more electrons to complete it's outer shell so in oxygen gas two atoms share two pairs of electrons with each other making a double covalent bond.

Nitrogen, N2

Nitrogen atoms need three more electrons so two nitrogen atoms share three pairs of electrons to fill their outer shells. This creates a triple bond.

Methane, CH4

Carbon has four outer electrons, which is half a full shell. It can form four covalent bonds with hydrogen atoms to fill up its outer shell.

Water, H2O

In water molecules, the oxygen shares a pair of electrons with two H atoms to form two single covalent.

Hydrogen Chloride, HCl

This is similar to H2 and Cl2. Again, both atoms only need one more electron to complete their outer shell.

What type of structures do substances containing covalent bonds usually have?

Simple molecular structures

What are some examples of simple molecular substances?

H2, HCl, H2O, CH4

What holds the atoms within simple molecular substances together?

Very strong covalent bonds

What type of forces exist between molecules in simple molecular substances?

Very weak intermolecular forces

What are the melting and boiling points of simple molecular substances like?

Very low

Why do simple molecular substances have low melting and boiling points?

Weak intermolecular forces are easy to overcome

What is the physical state of simple molecular substances at room temperature?

Gases or liquids

How does the size of molecules affect the strength of intermolecular forces?

As molecules get bigger, the strength of intermolecular forces increases

What happens to the melting and boiling points as the size of molecules increases?

They increase

Do simple molecular substances conduct electricity?

No, because they aren't charged and have no free electrons or ions

What are polymers?

Long chains of repeating units, small units are linked together to form a long molecule that has repeating sections

What is a polymer joined by?

Strong covalent bonds

What is a repeating unit?

A part of a polymer that would make a complete polymer molecule if many of them were joined end to end

How do you find the molecular formula of a polymer?

Write down the molecular formula of the repeating unit in brackets, and put an 'n' outside

Why are polymers solid at room temperature?

The intermolecular forces between polymer molecules are larger than between simple covalent molecules, so more energy is needed to break them.

Why do polymers have lower boiling points than ionic or giant molecular compounds?

The intermolecular forces are still weaker than ionic or covalent bonds

What are the atoms in a giant covalent structure bonded by?

All the atoms are bonded by strong covalent bonds

Why do covalent structures have a very high melting and boiling point?

Lots of energy is needed to break the covalent bonds between the atoms

Do covalent structures conduct electricity?

No because they don't contain charged particles not even when molten (except graphite)

What are the main covalent structures?

Diamond, graphite, silicon dioxide

Diamond

Each carbon atom forms four covalent bonds in a very rigid giant covalent structure

Graphite

Each carbon atom forms three covalent bonds to create layers of hexagons. Each carbon atom also has one delocalised electron.

Silicon dioxide

Sometimes called silica, this is what sand is made of. Each grain of sand is one giant structure of silicon and oxygen

What are allotropes?

Different structural forms of the same element in the same physical state

What are some common allotropes of carbon?

Carbon, graphite, fullerenes

How many bonds does the carbon atoms in diamond form?

Each atom forms four covalent bonds - makes diamond really hard

Why does diamond have a high melting point?

Large amounts of energy are needed to overcome their strong covalent bonds

Why does diamond not conduct electricity?

It has no delocalised electrons or ions

How many bonds does the carbon atoms in graphite form?

Each atom forms three covalent bonds - creates sheets of carbon atoms arranged in hexagons

How are the layers between graphite held together?

There are no covalent bonds between layers - they're only held together weakly, so they're free to move over each other

What makes graphite soft and slippery?

The layers are free to slide over each other because there are no covalent bonds between the layers

Why is graphite ideal as a lubricating material?

It's soft and slippery

Why has graphite got a high melting point?

The covalent bonds in the layers need loads of energy to break

Does graphite conduct electricity?

Yes it also conducts thermal energy, as only three out of each carbon's four outer electrons are used in bonds, so each carbon atom has one delocalised electron that can move freely throughout.

What is graphene?

A single layer of graphite

What shape is graphene joined together in?

Hexagons

How thick is graphene?

One atom thick, making it a two dimensional substance

Why can graphene be added to composite materials?

The network of covalent bonds makes it very strong, it's also incredibly light ----> added to composite materials = improving their strength without adding much weight

Can graphene conduct electricity?

Yes because it has delocalised electrons = has the potential to be used in electronics

What are fullerenes?

Molecules of carbon atoms shaped like closed tubes or hollow shapes

What are fullerenes made up of?

Mainly carbon atoms arranged in hexagons can also contain pentagons or heptagons

What are fullerenes used for?

To 'cage' other molecules by forming its structure around another atom or molecule, which is then trapped inside.

Used to deliver drugs into the body

Why do fullerenes have a huge surface area?

They could help make great industrial catalysts - individual catalyst molecules could be attached to the fullerenes

Are fullerenes lubricating?

Yes

What can fullerenes form?

Nanotubes - tiny carbon cylinders

What are properties of nanotubes?

-Conducts electricity and thermal energy

• Ratio between the length and the diameter of the nanotubes is very high

• A high tensile strength (don't break when stretched)

What is metallic bonding?

The electrons in the outer shell of a metal atom are delocalised. There are strong forces of electrostatic attraction between the positive metal ions and the negative electrons. These forces of attraction hold the atoms together in a regular structure.

What substances are held together with metallic bonding?

Metallic elements and alloys

What produces the properties of metals?

Delocalised electrons

Why do metallic substances have a high melting and boiling points?

The electrostatic forces between the meal atoms and the delocalised sea of electrons are very strong, so need lots of energy to be broken down

What does having a high boiling and melting point mean for metallic bonding state wise?

This means they are generally solid at room temperature

Why are metals good conductors of electricity?

The delocalised electrons carry electrical charge and thermal energy through the whole structure

Why are most metals malleable?

The layers of atoms in a metal can slide over each other

Why are alloys harder than pure metals?

Different elements have different sized atoms so when another element is mixed with a pure metal, the new metal atoms will distort the layers of metal atoms making it more difficult for them to slide over each other.

What are alloys?

A mixture of two or more metals

What are the three states of matter?

Solid, liquid, gas

What do the strong forces of attraction between particles depend on?

The material, the temperature, the pressure

What does aqueous mean?

Dissolved in water

What do the particles in a solid do?

Vibrate in place, the hotter the solid becomes, the more they vibrate

What do the particles in a liquid do?

Constantly move with random motion, the hotter the liquid gets the faster they move. This causes the liquids to expand slightly when heated

What do the particles in a gas do?

Move constantly with random motion. The hotter the gas gets, the faster they move. The gases either expand when heated, or their pressure increases