C2 - Bonding, Structure & Properties of Matter

What is an ion?

Ions are charged particles – they can be single atoms or a group of atoms

Why do atoms lose or gain electrons?

To gain a full outer shell

What are the three types of bonding?

Ionic Bonding, covalent bonding, and metallic bonding

What is ionic bonding?

The transfer of electrons from a metal (which loses electrons) to a non-metal (which gains electrons).

What type of ions do metals form?

Positively charged ions

What type of ion do non - metals form?

Negatively charged ions

What holds ionic compounds together?

The electrostatic forces between the oppositely charged ions in all directions, which are strongly attracted to one another

What structure do ionic compounds have?

A giant ionic lattice

Why are the boiling and melting points of ionic compounds high?

Because of the strong bonds between the ions, which require lots of energy to break

Do ionic compounds conduct electricity?

They can only conduct electricity when molten or dissolved, as ions are free to move and carry charge.

Not able to conduct when solid, as ions are held in place

Are ionic compounds soluble in water?

Some are as the ions separate and are free to move in solution

What are dot and cross diagrams?

Shows how electrons are transferred between atoms to form ions

Limitations of Dot and Cross diagrams

• They don’t show the structure of the compound
  

• They don’t show the size of the ions or how they are arranged

What is the ball and stick model?

Shows the 3D arrangement of ions in a lattice

Limitations of the ball and stick model

• The spacing between ions are too large; in reality, they are closely packed
  

• The sticks suggest physical bonds, but ionic bonds are electrostatic attractions
  

• The model only shows a tiny part of a lattice

What is covalent bonding?

When non-metal atoms share pairs of electrons 

What types of structures can covalent bonding form?

Simple molecular structures or giant covalent structures

What holds the atoms together in a covalent bond?

The strong electrostatic forces between the shared electrons

Why do covalent substances have low melting and boiling points?

Because weak intermolecular forces require little energy to be overcome

Why don’t simple covalent molecules conduct electricity?

Because they have no free electrons or ions

What is a polymer?

They are large molecules made of monomers joined by strong covalent bonds

What are giant covalent structures?

A substance made up of millions of atoms that are joined by strong covalent bonds, forming a giant lattice

Do giant covalent structures conduct electricity?

They usually don’t, except for graphite, which has free delocalised electrons

Describe diamond’s structure and its properties

• Each carbon atom forms 4 covalent bonds
  

• Very hard, high melting point, does not conduct electricity

Describe graphite’s structure and its properties

• Each carbon atom forms 3 covalent bonds in hexagonal layers
  

• Layers slide easily as they have weak intermolecular forces
  

• Conducts electricity due to delocalised electron
  

• High melting point

What is graphene?

A single layer of carbon atoms in a hexagonal lattice

Describe the structure of silicon dioxide and its properties

• Each silicon atom is bonded to 4 oxygen atoms
  

• Very hard and has a very high melting point
  

• Does not conduct electricity due to no delocalised electrons

What are fullerenes?

They are hollow shapes (spheres or tubes) formed by carbon atoms

What are some uses of fullerenes?

Lubricants

What was the first fullerene to be discovered?

Buckminsterfullerene (C60), which has a spherical shape

What are nanotubes?

They are tiny carbon cylinders

What are the properties of nanotubes, and how can they be used?

• Conducts electricity and thermal energy.
  

• Strong covalent bonds
  

• They have a high tensile strength (they don’t break when stretched). They have a low density
  

• Electronics, and for strengthening materials

What are some uses of nanoparticles?

Sunscreens, deoderants, , drug delivery

Why might nanoparticles be dangerous?

They can enter cells and cause harm

What is metallic bonding?

The electrostatic attraction between positive metal ions and delocalised electrons

Why do metals conduct electricity and heat?

Delocalised electrons move freely and can carry charge

Why do metals have high melting and boiling points?

Strong metallic bonds need lots of energy to break

Why are metals malleable and ductile?

Because layers of atoms can slide over each other

What are alloys?

Alloys are a mixture of two or more metals

How are alloys different from pure metals?

They contain atoms of different sizes, which distorts the layers of the atoms, and this makes alloys harder than pure metals

What are the three states of matter?

Solid, liquid, and gas

Describe the arrangement of particles in a solid

• They are closely packed together in a fixed, regular arrangement (cannot be compressed)
  

• Held in place by strong forces of attraction
  

• They vibrate in fixed positions

Describe the arrangement of particles in a liquid

• The particles are randomly arranged and move past each other, but still close (cannot be compressed easily)
  

• They have no fixed shape and will flow to fill a container
  

• Held together by weak force of attraction between particles

Describe the arrangement of particles in a gas

• The particles are very far apart (can be compressed easily)
  

• They are arranged randomly and move quickly in all directions
  

• The forces of attraction are very weak

What changes occur when substances melt, boil, condense, or freeze?

• Melting or boiling – energy is transferred to the particles (breaks bonds)
  

• Condensing or freezing – energy is transferred from particles (makes bonds)

What happens to the temperature during a change of state?

It stays constant while the substance changes state

What is the difference between physical and chemical changes?

• Physical changes can be reversed
  

• Chemical changes form new substances and are not easily reversible

What do the following state symbols mean?

(s) = Solid, (l) = Liquid, (g) = Gas, (aq) = aqueous (dissolved in water)