Bonding,Structure and Properties of Matter

What is ionic bonding?

• the electrostatic attraction between positive and negative ions, which is a relatively strong attraction

How are ionic compounds held together?

• held together in a giant ionic lattice

• regular structure that extends in all directions in a substance

What are the properties of ionic substances?

• high melting and boiling points (strong electrostatic forces between oppositely charged ions) because of the amount of energy needed to break the bonds

• do not conduct electricity when solid

• conduct when molten or dissolved in water because ions are free to move so charge can flow

• have regular structures

Describe ionic bonding

• metal and non metal react, electrons in outer shell of the metal atom are transfers

• metals lose electrons => positive ions

• non-metals gain electrons => negative ions

• strong electrostatic force between opposing charges

What is a covalent bond?

• a shared pair of electrons between two atoms

What is the structure and properties of simple molecular covalent substances?

• do not conduct electricity (no ions)

• small molecules

• weak intermolecular forces which require little energy to overcome

• low melting and boiling points

What is metallic bonding?

• the electrostatic attraction between the positive metal ions and the negative delocalised electrons

How does metallic bonding occur?

• electrons in the outer shell of the metal atoms are delocalised so they are free to move around.

• there are strong electrostatic bonds between the positive metal ions and the shared negative electrons

Why are most metals solid at room temp?

• the electrostatic forced between the metal ions and delocalised sea of electrons are very strong, so need lots of energy to be broken

• meaning they have very high melting and boiling points

Why are metals good conductors of heat and electricity?

• the delocalised electrons carry electric charge and thermal heat energy through the whole structure, so metals are good conductors of electricity and heat

Why are most pure metals malleable?

• the layers of atoms in a metal can slide over each other

Why are alloys harder than pure metals?

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

Why are alloys sometimes used instead of pure metals?

• they are often too soft

• alloys are harder and therefore more useful

What element are diamond and graphite made up of?

• carbon

State the properties and structure of diamond

• each carbon atom is covalently bonded to 4 others

• hard - many strong covalent bonds in the structure

• high melting point - bonds require lots of energy to overcome

• poor electrical conductivity - no delocalised electrons to move and carry charge

state the properties and structure of graphite

• each carbon atom is covalently bonded to 3 others forming layers of hexagonal rings which have no covalent bonds between the layers

• soft - weak forces between layers so they can slide over each other

• good electrical conductivity - each atom has a delocalised electron that can move and carry charge through the structure

What is a nanometer?

• a unit of length in the metric figure system, equal to one billionth of a meter

• 10^-9 meters

What is a nanoparticle?

• very small particles

• range from 1-100nm

• small so very reactive

• they are so small that their properties can change

What are some uses for nanoparticles?

• sunscreen, nanoparticles of zinc oxide or titanium are used to block UV rays from the sun

• Cosmetics. can be used as they absorb deeper into the skin

• Medicine, gold nanoparticles can be used to treat cancerous tumours, carbon nanocages can transport drugs around the body

• Sports Equipment, create strong but lightweight sports equipment

• Antibacterial, silver nanoparticles prevent growth of bacteria, can be used in fridges, sprays, used to clean hospitals and even clothing

• catalysts

Describe an ionic compound

• giant ionic structure, held together by strong electrostatic forces of attraction between opposing charges

• forces act in all directions in the lattice

What is graphene?

• a single layer of graphite

What are fullerenes?

• molecules of carbon atoms, hollow spaces

• based on hexagonal rings of carbon atoms, may contain rings with five or seven carbon atoms

• buckminsterfullerene has a spherical shape