Chemistry Sc5, Sc6, Sc7 - Bonding, structures, properties (Year 9 Spring term)

ion

an atom or groups of atoms with an electrical charge due to the gain/loss of electrons

Cation

A positively charged ion

Anion

A negatively charged ion

Ionic bonding is between

metals and non-metals

electrostatic forces

forces of attraction between oppositely charges particles

what happens to the ending of non metal ions

add -ide (oxygen > oxide)

Ionic Compound

No overall charge (neutral) e.g Aluminium Chloride

-ide compounds

contain only 2 elements

-ate compounds

contain oxygen and 3 or more elements

Polyatomic ions

groups of 2 or more atoms which have become charged

Ammonium

NH₄+

Nitrate

NO_3^-

Hydroxide

OH^-

Carbonate

CO_3^2-

Sulfate

SO_4^2-

Sulfite

SO_3^2-

ion arrangement

packed together in a regular repeating arrangement cfalled a LATTICE

• alternating cations and anions

• held together by electrostatic forces

Properties of Ionic Compounds

-high melting/ boiling points -require lots of energy to break -Only conduct electricity when molten or aqueous as the ions are free to move

• many soluble in water

• hard but brittle

covalent bond

a shared pair of electrons

what does covalent bonding occur between

non-metals

Valency

How many covalent bonds an atom will make 8 - group number = valency

How are molecules held together

atoms in molecules are held together by strong electrostatic forces of attraction between the positive nuclei and the negative electrons

Simple Molecular (covalent) structure

small distinct groups of atoms

Giant covalent structure

billions of atoms held together in a lattice structure

simple molecular properties

• low melting/boiling points

• a few are soluble in water

• most do not conduct electricity

why do simple molecules have low melting/boiling points

because it does not take much energy to overcome weak intermolecular forces

why do simple molecules not conduct electricity

Because molecules are neutral so cannot carry charge

Giant covalent properties

• high melting/boiling points

• do not conduct electricity ( apart from graphite and graphene due to delocalised electrons)

• insoluble in water

polymer

monomers joined in a chain -longer polymers have more intermolecular forces -> higher melting/boiling points

Diamond (Structure, Properties, Uses)

Structure- giant covalent Properties: -high melting point -insoluble in water -does not conduct electricity (no free electrons) -4 strong covalent bonds Uses: used in cutting tools (hard)

Fullerene (structure, properties, uses)

Structure - simple molecule

-low melting point

-soft + slippery

-does not conduct electricity (delocalised electrons can't move between molecules)

-3 covalent bonds

Uses: carbon nanotubes can conduct electricity (electronics)

Graphite

structure - giant covalent (layers of graphene) -high melting point

• insoluble in water

• good conductor(layers allow delocalised electrons to be free to move)

• Uses: electrodes in electrolysis, pencil leads (slippery)

Graphene structure, properties and uses

structure: giant covalent- single layer sheets of carbon in hexagonal lattice

-high melting point -very strong

-good conductor of electricity (delocalised electrons)

Uses: added to plastics/carbon fibre (strong)

typical properties of metals

-solids with high melting points

-shiny

-malleable

-high density

-good conductors of electricity

typical properties of non-metals

-solid/liquids/gases with low melting point -brittle -low density

• poor conductors

why are metals malleable

because layers of ions can slide over each other

why can metals conduct electricity

because delocalised electrons flow through the structure carrying a charge

delocalised electrons

not associated with a particular atom or bond

metallic bonds

strong electrostatic forces of attraction between positive metal ions and negative delocalised electrons

metal structure

giant metal lattice -electrons in the outer shell are delocalised > move throughout the structure -metal atoms are + since they lose electrons