1.3 Structures

Delocalised electrons

Delocalised electrons

an electron that is able to move freely and carry charge

Positive metal ions are

Metal atoms that have lost their outer electrons

Lattice

Regular arrangement of particles

Giant structure

A huge 3D network of atoms or ions

Electrostatic forces of attraction

Strong forces of attraction between oppositely charged particles

Metallic bonding

A lattice of positive metal ions surrounded by delocalised outer electrons, held together by strong electrostatic forces of attraction

Melting and boiling points of metallic substances

high as strong electrostatic forces between positive metal ions and negative delocalised electrons

Reason for metals being malleable

Layers of metal ions can slide over each other

Reason alloys are harder than pure metals

Different sized atoms disrupt the layers of ions, preventing layers from sliding

Usefulness of pure metals

Too soft for most uses

Reason metals conduct heat well

delocalised electrons can transfer heat energy quickly

Reason metals conduct electricity well

delocalised electrons can carry electrical charge through the structure.

24 carat gold

pure gold

Gold used in jewellery is

Usually an alloy with silver, copper and zinc

18 carat gold

An alloy containing 75% gold

12 carat gold

An alloy containing 50% gold

Giant structure

A three-dimensional network of atoms or ions

Lattice

Regular arrangement of particles.

Bonding in giant covalent structures

Covalent bonding

Covalent bond

A shared pair of electrons

States of giant covalent substances at room temperature

Solid

Melting points of giant covalent substances

Very high

Bonds broken when giant covalent structures are melted

Covalent bonds

Examples of giant covalent structures

Diamond, graphite, silicon dioxide

Reason for giant covalent structure's high melting point

Many strong covalent bonds require lots of energy to break

Solubility of giant covalent substances

Insoluble

Formula of silicon dioxide

SiO₂

Uses of diamond

Cutting tools and jewellery

Uses of graphite

Pencil leads, lubricants

Number of bonds between atoms in graphite

3

Properties of diamond

Translucent, Hard, High melting point, Does not conduct electricity

Properties of graphite

Soft, Slippery, good conductor of heat and electricity

Reason graphite is soft

Weak forces between layers which can slide over each other.

Reason graphite conducts electricity

One spare electron is delocalised and can carry charge through the layers

Molecule

Two or more atoms held together by covalent bonds

State of molecular substances at room temperature

Liquids or gases

Van der Waals forces

Weak forces of attraction between molecules

Melting and boiling points of molecular substances

Low as Van der waals forces are weak.

Trends in Van der Waals

The larger the molecule the stronger the Van der Waals

Electrical conductivity of molecular substances

Low conductivity

Reason for electrical conductivity of molecular substances

Molecules are neutral

Covalent bonds

A shared pair of electrons

Solubility of small molecules

Insoluble in water

Soluble molecules

Hydrochloric acid, ammonia

Reason some molecules are soluble

They react with water

Giant ionic lattice

huge 3D regular structure held together by the electrostatic forces of attraction between positive and negative ions

Melting and boiling points of ionic substances

high

Reason for melting and boiling points of ionic substances

Strong ionic bonds and electrostatic forces require substantial energy to break

Movement of ions in a solid

Ions vibrate around fixed positions

Molten

Made liquid by heat

Movement of ions when molten

Ions can move past each other

Movement of ions in solution

Ions break apart and move freely

Conductivity of solid ionic compounds

don't conduct

Reason for conductivity of solid ionic compounds

Ions are fixed in place

Conductivity of molten/dissolved ionic compounds

good conductors

Reason for conductivity of liquid/dissolved ionic compounds

Ions are free to move and carry charge

Electrostatic force of attraction

attractive force between oppositely charged particles

Number of bonds between atoms in diamond

4

Allotrope

Different forms of the same element in the same state

Number of bonds between atoms in graphite

3

Properties of graphite

Soft, Slippery, good conductor of heat and electricity

Properties of graphene

Very strong and flexible, good thermal and electrical conductor, nearly transparent

Reason graphene conduct electricity

One spare electron is delocalised and can carry charge through the layer

Graphene

A single layer of graphite one atom thick.

Uses of graphene

Electronics and solar cells

Reason graphene is strong

Strong covalent bonds between atoms need lots of energy to break

Carbon outer shell electrons

4

Carbon maximum covalent bonds

4 - sharing all its outershell electrons

Reason for metals high melting and boiling points

strong electrostatic forces between positive metal ions and negative delocalised electrons

Reason metals being malleable

layers of ions can slide over each other

Reason alloys are harder than pure metals

Different sized atoms disrupt the layers of ions, preventing layers from sliding

Usefulness of pure metals

Too soft for most uses

Reason metals conduct heat well

Delocalised electrons can transfer heat energy quickly.

Reason metals conduct electricity well

Delocalised electrons can carry electrical charge through the structure.