[0] Types of bonding

What structure do ionic compounds form?

A giant three-dimensional ionic lattice.

Why do ionic compounds have high melting and boiling points?

Strong electrostatic attractions act between oppositely charged ions throughout the lattice, requiring a large amount of energy to overcome.

Why are ionic compounds brittle?

If layers shift, ions with the same charge are brought together and repel, causing the lattice to split.

Why do molten ionic compounds conduct electricity?

Their ions are free to move and carry electrical charge.

Why do ionic compounds conduct electricity when dissolved in water?

The dissolved ions are free to move through the solution and carry charge.

What is a simple molecular substance?

A substance consisting of separate molecules with strong covalent bonds within each molecule.

What forces exist between simple molecules?

Intermolecular forces.

Are covalent bonds broken when a simple molecular substance melts?

No; only the intermolecular forces between the molecules are overcome.

How does molecular size generally affect boiling point?

Larger molecules normally have stronger intermolecular forces and therefore higher boiling points.

What is a giant covalent structure?

A large network of atoms joined by many strong covalent bonds.

Why do giant covalent substances have high melting and boiling points?

Many strong covalent bonds must be broken, requiring a large amount of energy.

Why is diamond very hard?

Each carbon atom is joined to four others in a rigid three-dimensional giant covalent lattice.

Why does diamond not conduct electricity?

All four outer electrons from each carbon are used in covalent bonds, so there are no mobile charged particles.

How many covalent bonds does each carbon atom form in graphite?

Three covalent bonds.

Why is graphite soft and slippery?

It consists of layers held together by weak forces, allowing the layers to slide over one another.

Why does graphite conduct electricity?

Each carbon provides one delocalised electron that can move through the layers and carry charge.

What type of structure does silicon dioxide have?

A giant covalent lattice.

Why does silicon dioxide have a high melting point?

Many strong covalent bonds must be broken.

Why does silicon dioxide not conduct electricity?

It has no mobile ions or delocalised electrons.

What happens to the outer electrons in metallic bonding?

They become delocalised and move throughout the metal structure.

What structure is found in a metal?

A regular lattice of positive metal ions surrounded by delocalised electrons.

Why do metals conduct electricity when solid?

Their delocalised electrons are free to move through the structure and carry charge.

Why can metals conduct electricity when molten?

The delocalised electrons remain mobile and can carry charge.

Why do metals conduct thermal energy?

Mobile delocalised electrons transfer energy rapidly throughout the structure.

Why are metals ductile?

Their layers can slide without the metallic bonds completely breaking, allowing metals to be drawn into wires.

What is the role of electrons in metallic bonding?

Outer electrons become delocalised and attract the positive metal ions together.

Which bonding types involve electrostatic attraction?

All three: between opposite ions in ionic bonding, nuclei and shared electrons in covalent bonding, and positive ions and delocalised electrons in metallic bonding.

Which substances conduct electricity using mobile ions?

Molten ionic compounds and ionic compounds dissolved in water.

Which substances conduct electricity using delocalised electrons?

Metals and some giant covalent substances such as graphite and graphene.

What is the correct explanation for the high melting point of an ionic compound?

It has a giant ionic lattice with strong electrostatic attractions between oppositely charged ions, requiring a large amount of energy to overcome.

What is the correct explanation for the low boiling point of a simple molecular substance?

Only the relatively weak intermolecular forces between molecules are overcome, requiring little energy.