CHEMISTRY TOPIC 2- Bonding, Structure, and Properties of Matter

Bonding, Structure, and Properties of Matter

Ions and How they’re Formed

Charged particles

Formed when elements lose or gain electrons to gain a full outer shell

Electrons are transferred to other element in ionic bonding to fill their outer shell also

Full outer shell = very stable and inert

When forming ions, the quickest/easiest method of making a full outer shell will be used e.g. group 6 elements could lose 6 electrons or just gain 2

Cations and Anions

Cations are positive ions

Anions are negative ions

How Metals form Ions

Metals lose electrons from outer shell to form cations (positive)

How Non-metals form Ions

Non-metals gain electrons to outer shell to form anions (negative)

Groups most Likely to form Ions

Groups 1, 2, 6, 7

They need to gain/lose few electrons to achieve a full outer shell

Charge of an Ion in Group 1

Group 1 elements have 1 electron in outer shell, so they need to lose one electron to form an ion

This means they are misusing 1 negative charge (- - 1)

-- - 1 = +1 , so group 1 elements form 1+ ions

Charge of an Ion in Group 6

Group 6 elements have 6 electrons in outer shell, so need to gain 2 electrons to form an ion

This means they are adding 2 negative charge (+ - 2)

+ - 2 = -2 , so group 6 elements form 2- ions

Ionic Bonding

Transfer electrons between elements to give both full outer shells

Between metal and non-metal

Metal atoms transfer ions to non-metals

Strong intermolecular forces

Oppositely charged ions provide strong electrostatic forces

Ionic Compound Structure

Giant Ionic Lattice Structure

Regular arrangement of ions held together by strong electrostatic forces and ionic bonds

Ionic Compound Properties

High melting and boiling points due to strong ionic bonds

Only conduct electricity when molten or dissolved in solution (ions cannot move and carry a current when solid)

Strong intermolecular forces

Covalent Bonding

Share electrons between elements to give both full outer shells

Between non-metal and non-metal

Very strong covalent bonds- positive nucleus attracted to shared pair of electrons by electrostatic forces

Only outer shell electrons are shared

These bonds can form single, double, or triple bonds depending on the number of shared electron pairs e.g. one pair of electrons shared = one bond

Ways to Draw Covalent Bonds

Dot and Cross diagrams

Displayed Formula e.g. H — Cl

3D Model

Examples of Simple Molecular Substances

All have simple single covalent bonds

Hydrogen, H₂

Chlorine, Cl₂

Oxygen, O₂

Nitrogen, N₂

Methane, CH₄

Water, H₂O

Hydrogen Chloride, HCl

Carbon Dioxide, CO₂

Simple Molecular Substance Properties

Contain very strong covalent bonds

Contain very weak forces of attraction ( same charge molecules)

Low boiling points usually- only need to break week intermolecular forces, not the strong covalent bonds

As molecules get bigger, intermolecular forces increase (boiling point increases since more energy need to break forces)

Most are gas/liquid at room temperature

Don’t conduct electricity- no free electrons/ions

Polymers

Long chain of repeating units (monomers)

Atoms joined by covalent bonds

Molecular formula for polymer = (repeating unit)_n where n is the number of repeats

Large intermolecular forces- most are solid at room temperature and high boiling points

Lower boiling points than ionic and giant molecular compounds

Giant Covalent Structures / Macromolecules

Atoms bonded by strong covalent bonds

Very high melting and boiling points- lots of energy required to break bonds

Don’t conduct electricity (except for exceptions e.g. graphite with delocalised electrons)

Giant Covalent Bonds Examples

Diamond- each carbon atom has 4 covalent bonds

Graphite- each carbon forms 3 covalent bonds, made of layers of graphene which can slide over one another due to weak intermolecular forces; also conductive (each carbon has 1 delocalised electron)

Silicon Dioxide (Silica) - sand

Allotropes of Carbon

Different structures of carbon giving varying properties in the same state

Diamond- very hard due to each carbon having 4 covalent bonds, high melting point, nonconductive

Graphene- layer of graphite, sheet of carbon atoms joined to make hexagons, light, strong, conductive due to delocalised electrons from carbon

Graphite- each carbon has 3 covalent bonds, organised in sheets of graphene made of hexagons, conductive due to delocalised electrons meaning it can be used in electronics

Fullerene- structured in ball-like or tube shapes; arranged in pentagons, hexagons, or heptagons. Can be used to cage molecules and deliver drugs to body. Large surface area so useful for industrial catalysts. Can be used as lubricant. Form nanotubes (conductive, high tensile strength, used in electronics or strengthening without adding weight)

Metallic Bonding

Positively charged metals bond in a sea of their delocalised electrons keeping them bonded due to the electrostatic forces between the negative electrons and positive metal atoms/ions

Between metal and metal

Outer shell electrons delocalised, meaning high conductivity and strong electrostatic forces

Properties of most Metals

Solid at room temp

Malleable (bendable)- metal layers can slide over one another

Good electric and thermal conductors

Ductile (can be drawn into wires)

High melting and boiling points

Alloys

Mixture of metals

Better stability

Atoms in alloy have different sized atoms, meaning the layers are distorted so they can’t slide over each other as easy (harder than pure metals)

Higher boiling points

Solids

State symbol (s)

Strong forces of attraction between particles

Forces hold particles in fixed positions in regular lattice arrangement

Keep definite volume and shape

Particles vibrate in fixed positions (heat increases vibrations, causing expansion)

Liquids

State symbol (l)

Weak forces of attraction between particles

Random arrangement, free to move past one another but stay close together

No definite shape/volume- liquids flow to fill bottom of container

Constant movement with random motion (heat increases speed, leads to expansion)

Gases

State symbol (g)

Very weak forces of attraction between particles

No fixed arrangement, particles free to move

Particles travel in straight lines

No definite shape or volume, always fills container

Constant random movement (heat increases movement speed leading to further expansion)

Heat and pressure increase lead to gas expanding

Changing State: Solid → Liquid

Melting

Changing State: Liquid → Solid

Freezing

Changing State: Liquid → Gas

Boiling / Evaporation

Changing State: Gas → Liquid

Condensing

Changing State: Solid → Gas

Sublimation

Changing State: Gas → Solid

Deposition