Chemistry covalent and metallic bonds

What are metals?

Elements that can form positive ions

Name 5 typical physical properties of metals

Malleable, ductile, conduct heat, conduct electricity, high melting points

What is the structure of metals?

A giant structure of positive metal ions surrounded by a sea of delocalised electrons

What is metallic bonding?

Strong electrostatic attraction between positive metal ions and delocalised electrons

Why do metals have a high melting point?

Giant lattice of strong metallic bonds which require a lot of energy to break

Why do metals conduct electricity?

Delocalised electrons that are mobile and can carry charge through the structure

Why do metals conduct thermal energy?

When their delocalised electrons collide in the metal, they transfer energy

Why are metals malleable?

When a force is applied to a metal, the layers of ions slide over each other

Why are metals ductile?

When force is applied to either end of a metal, the layers of ions slide over each other repeatedly in opposite directions

What is a covalent bond?

The electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms

How do two non-metal atoms combine?

By sharing electrons

What type of atoms combine using covalent bonds?

Non-metals

How does a covalent bond form?

Two non-metals atoms share electrons

Name two types of covalent structure

Simple molecular and giant covalent

What is a simple molecular structure?

Consists of small molecules

In a simple molecular structure what type of bond is found within the molecules?

Covalent

What is an intermolecular force?

A weak attraction between molecules

When a simple molecular substance melts, what is overcome?

Intermolecular forces, the molecules separate from one another

What happens to covalent bonds when a simple molecular substance melts?

Nothing they remain

What is a giant covalent structure?

A regular 3D structure consisting of many non-metal atoms bonded together by covalent bonds

Name three giant covalent structures

Diamond, graphite,silicon dioxide and Graphene

Described diamond

Each carbon atom is covalently bonded to 4 other carbon atoms, hard, high melting lint, does not conduct electricity

Described graphite

Each carbon atom is covalently bonded to3 other carbon atoms. Soft, slippery, high melting point, conduct electricity.

Why is graphite soft.

Has layers of carbon in hexagons which can slide because they are held by weak intermolecular forces.

Why does graphite conduct electricity?

Mobile delocalised electrons carry charge through the structure

Why do diamond and graphite have high melting temperatures?

Many string covalent bonds must be broken

What is graohene

? A single layer of graphite

Give two properties of graihene

Conducts electricity, very strong

What can graohene do?

Upload a movie in 10 seconds, charge your phone in 1 minute, absorb radioactive compounds, and medical treatment

What is fullerene?

Molecules of several carbon atoms with hollow shapes.

What is C60 called?

Buckminsterfullerene

What shapes can fullerene be?

Tubes or spheres

What is a nanotube?

A cylindrical fullerene

Give two properties of nanotubes?

Very strong, conducts electricity

Give three uses of fullerenes

Lubricants, drug delivery and electronics

Why can spherical fullerenes be used a lubricants?

They can roll

What is an allotrope?

A different physical structure of an element

Name 4 llotropes of carbon

Diamond, graphite, graphene and fullerene

Why is diamond very hard?

Diamond has layers of carbon in hexagons where each carbon covalently bonds to 4 others. These require lots of energy so are very difficult to break down

What is metallic bonding?

The strong electrostatic force of attraction between the positively charged metals ions and the negatively charged delocalised electrons

Why does iodin have a low melting point?

It’s a simple molecule, so only a small amount of energy is needed to break the weak intermolecular forces.

Explain why calcium fluoride (an ionic bond) has a high melting point?

Simple molecule, Strong ionic bond between Ca plus 2 and F minus oppositely charged ions. In a giant lattice structure so a lot of energy is needed to break this attraction