Chemistry unit 2.1 bonding, structure and properties

What are the 3 types of chemical bonds?

Ionic, metallic and covalent

What is metallic bonding?

When metal atoms bond together

-the attraction between the positive metal ions and negative electrons is strong and holds structure together

What are the properties of metallic compounds?

• high melting and boiling points- strong bonds, to melt or boil metals you have to overcome the strong forces. Lots of energy required

• good conductors of electricity- free electrons can move through the structure carrying a charge

• good conductors of heat- electrons move faster when heated so the metal ions vibrate faster and quickly transfer the heat through metal structures

• malleable and ductile- layers of metal ions can slide over each other without breaking the metallic bond

What is ionic bonding?

Metals with non metals

Why do ionic bonds happen?

Ionic bonds form when electrons transfer from a metal to a non metal so both atoms gain full outer shells

What are the properties of ionic compounds?

• strong electrolytic attraction between charged ions means ionic compounds have high melting and boiling points

• in a solid state, ionic compounds do not conduct electricity as the ions are fixed in place

• when molten/dissolved ions can move around so then ionic compounds conduct electricity

• they are brittle

What is covalent bonding?

Bonding between non metal atoms

How does covalent bonding happen?

They share electrons so both atoms achieve full outer shells

What are the properties of giants ionic structures

•high melting and boiling points- lots of strong bonds between oppositely charged ions

• only conduct electricity when dissolved or molten - solid (not free to move)), when molten and dissolved ions can move

• soluble in water- charged water particles can attract charged ions away from the lattice

What are the properties of simple covalent structures? - only contain a few atoms

• low melting and boiling points- weak intermolecular forces. Not much energy needed to break the bonds

• do not conduct electricity- no free electrons to carry current

What are giant covalent structures?

Consist of lots of atoms held together by covalent bonds- arranged into giant lattices, which are extremely strong because of the number of bonds in structure

All forms of element carbon

What are the three types of giant covalent structures?

Diamond, graphite, carbon nanotubes

What are the properties of a diamond?

• very hard- lots of energy needed (each carbon bonds to 4 others)

• very high melting and boiling points- lots of energy needed

• cannot conduct electricity- no free electrons or ions to carry the charge

• used in jewellery, cutting glass

What are the properties of graphite?

• soft and slippery- layers can easily slide over each other. Weak forces of attractions easily broken

• conducts electricity- only non metals that can. Free electrons from each carbon that each layer has delocalised electrons that can carry charge

• used in pencils and lubricant

What are the properties and uses of carbon nanotubes?

• very high tensile strength, good heat conductance due to the delocalised electrons present

•uses- waterproof, tear resistant fabrics. Modified carbon nanotubes can enter cells and deliver drugs

What are fullerenes?

• molecules of carbon atoms with hollow shapes

• based on hexagonal rings of carbon atoms, but they may also contains rings with five or seven carbon atoms

What are the properties of nano particles?

• particles range from 1nm- 100nm

• contain a few hundred atoms

• they have different properties from bulk properties which they form because of their high surface area to volume ratio

What are examples of nano particles?

Nano- silver and nano titanium dioxide

What is Nano silver used for?

It’s anti fungal, anti- viral and anti- bacterial

• plasters, septic sprays, deodorant

What is nano-titanium dioxide used for?

It reflects sunlight

• sun cream, self-cleaning windows as they help break down dirt

What are the issues with nano particles?

• aren’t aware of the long term effects of them on the body as they are so small they could potentially enter bloodstreams and can enter and potentially damage environment

What is a smart material?

A material that changed properties based on environment. Changes are reversable

What are the properties and uses of thermionic properties?

• change colour when reach a certain temperature

• used in baby spoons and thermometers

What are the properties and uses of photochromic materials?

• change colour due to light intensity

• used in sunglasses

What are the properties and uses of hydrogels?

• can absorb up to 1,000 times their volume in water

• used in nappies and hair gel

What are the properties and uses of shape memory alloys?

• materials that regain shape when heated to a certain temperature

• glasses frames

What are the properties and uses of shape memory polymers?

Plastic materials that regain shape when heated to certain temperature

• used for self tightening stitches to close wounds