topic 2 - Bonding, Structure, and The Properties of Matter

What is ionic bonding?

Electrostatic attraction between positive and negative ions

Relatively strong attraction

How are ionic compound held together?

Held together in a giant lattice

Regular structure extends an all directions in a substance

Electrostatic attraction between positive and negative ions towards structure together

State properties of ionic substances

High melting and boiling point

Do not conduct electricity and solid

Conduct when molten or dissolved in water and ions are free to move

How are ionic compounds formed explain in terms of magnesium oxide?

Reaction of a metal with a non-metal

Electron transfer of occur and the metal gives away its outer shell and electrons to a nonmetal

Magnesium is in group 2 says two available outer shell electrons

Oxygen is in group 6 so it can accept two electrons to get a full outer shell configuration

Magnesium becomes 2+ an oxygen becomes two minus

What is a covalent bond?

A shared pair of electrons between two atoms

Describe the structure and properties of simple molecular covalent substances

Do not conduct electricity

Small molecules

Weak intermolecular forces therefore low melting and boiling points

How do intermolecular forces change as the size of the molecule increases?

They increase, causing melting and boiling points to increase as well as more energy is needed to overcome these forces

What are polymers and what are the Thermo softening polymers?

Polymers are very large molecules with atoms linked by covalent bonds

The softening polymers are special type of polymer which melt or soften when they're heated. They have weakened to molecular forces to ensure that the structure is solid at room temperature.

What are giant covalent substances?

Solids, atoms covalently bonded together in a giant lattice

High melting and boiling points due to strong covalent bonds

Mostly don't conduct electricity as they have no delocalised electrons

Diamond graphite and silicon dioxide

Describing and explain the properties of allotropes of carbon(diamond)

Diamond: four strong covalent bonds for each carbon atom

Very hard

High melting point due to strong bonds

Does not conduct electricity as there are no delocalised electrons

Graphite

Three covalent bonds for each carbon atom

Layers of hexagon rings

High melting point

Layers of free to slide as weak into molecular forces

Soft and can be used as a lubricant

Conduct thermal and electricity due to one delocalised electron by each carbon atom

Fullerenes

Hollow shaped molecules

Based on hexagonal rings, but may have 5 to 7 carbon rings

C. 60 has spherical shape simple molecular structure(buckminster fullering)

Nanotubes

Cylindrical fluorine with high length to diameter ratio

High tensile strength due to strong bond

Conductivity due to delocalised electrons

Graphene

Single layer of graphite

What is metallic bonding?

Forces of attraction between delocalised electrons and nuclei of metal ions

Describe properties of metals

High melting boiling points due to strong forces of attraction

Good conductors of heat and electricity due to delocalised electrons

Malleable and soft as the layers of atoms can slide over each other whilst maintaining the attraction forces

What are alloys? Why are they harder than pure metals?

Alloys or mixture of metal metals with other elements usually metals

Different sizes of atoms distort the layers so they can't slide over each other therefore allies are harder than pure metals

Simple covalent bonding

Melting and boiling point: low because of weak into molecular forces between molecules

Conductivity when solid: poor conductivity as there are no ions to conduct

Conductivity when molten; no ions

General description: mostly gases and liquids

Ionic bonding

Boiling and melting points: high because of the giant lattice of ions with strong forces between oppositely charged ions

Conductivity once solid: poor because the ions can't move

Conductivity once liquid; good because the ions are free to move

General description; crystalline solids

Giant covalent

Melting and boiling points: high because many strong covalent bonds between atoms and giant structure

Conductivity one solid: diamond and sand are poor because electrons can't move but graphite is good as 3-D localised electrons between layers can move through the structure

Conductivity when molten: poor

General description: solids

Metallic

Melting and boiling points: high, strong electrostatic forces between positive ions and delocalised electrons

Conductivity when solid: good as delocalised electrons are free to move through the structure

Conductivity when molten: good

General description: shiny metal solids

Limitations of the simple model

No forces between spares and atoms molecules and ions are solid spheres. This is not true.

Amount of energy needed to change state from solid to liquid or liquid to gas depend on

The strength of the forces between the particles of the substance. The nature of the particles involved depend depends on the type of bonding and the structure of the substance. The stronger the forces between the particles, the higher the melting point and boiling point of the substance.

A pure substance with melt or boil at? What about the mixture?

Pure substance will melt or boiler a fixed temperature and a mixture will melt over a range of temperatures

State the use of nano particles

Medicine drug delivery

Electronics

Deodorant 

suncream

What are fine and course particles

Find particles 100-2500 nm in diameter

Course particles - 2500 - 10^5 nm diameter

Why do non-particles have different properties to those for the same material in bulk

High surface area to volume ratio