Chemistry

Types of Bonding

A covalent bond occurs when two atoms share electrons from their outermost shell.

One covalent bond constitutes 2 electrons.

Chemistry Revision

Experimental Design and Purification Techniques

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To separate insolube solid from solution

To separate solute from solvent (to retrieve solute, from saturated solution after heating)

To separate and identify different substances in a mixture

To separate solute from solvent (to retrieve solute, heated to dryness)

To separate a mixure of two miscible liquids with distinctly different boiling points

To separate insoluble solids from solution (either to retrieve residue or filtrate)

To separate solute from solvent (to retrieve solvent)

To separte a mixture of solids, of which one sublimes

To separate a mixture of immiscible liquids

Atomic structure

Rf (retention factor) =

distance traveled by chemical/solvent front

Filtration

Solubility

ability to move with the mobile phase (solvent)

Adsoption

ability to attract to the stationary phase (paper)

Evaporation

Sublimation

Crystallisation

Chromatography

Simple distillation

Separating funnel

Fractional distillation

covalent bonding

Centrifuging and Decanting

metallic bonding

Simple Covalent Bonds

Giant Covalent Bonds

Diamond

3700 degree Celsius

Properties

3.5 g/cm^3

Melting point

Graphite

Colourless, transparent crystals

Density

3300 degree Celsius

Appearance

Hardest natural substance known; used as drill tips for drilling equipment and in glass cutters.

2.2 g/cm^3

Hardness

Black, shiny powder

Non-conductor

Electrical conductivity

Soft. Used as a solid lubricant to reduce friction in engines, and also used as pencil lead

Elements, Compounds &and Mixtures

Dative Covalent Bonds

Conductor

A substance that is made up of only one type of atom. It cannot be chemically split into simpler substances.

A substance that contains two or moresubstances physically together but not reacted with one another chemically.

A substance that contains two or more elements chemically joined together.

A coordinate bond or a dative covalent bond is a covalent bond in which the shared pair of electrons is provided by only one of the atoms.

• Metal ions held together by a 'sea' of free-moving delocalised electrons.
• Strong electrostatic forces between metal ions and 'sea' of electrons.

Van der Waals Forces

Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons

Greater electroneativity, greater pull on the electrons.

Asymmetrical distribution of electrons in electron cloud.

Interaction between polar molecules.

Polarity is due to the electronegativity of each atom in a molecule.

intermolecular bonds

Hydrogen Bonding

Hydrogen bonding occurs when a hydrogen atom is covalently bonded to oxygen or nitrogen. Such a hydrogen atom becomes attracted to the oxygen or nitrogen atom of a neighbouring molecule.

ionic bonding

• Metals + Non-metals
• Metal atoms lose electrons to form cations and non-metals gain electrons to form anions.
• Ions (cations & anions) are held together by strong electrostatic force of attraction

Properties

Metallic Structures

Giant molecules

Simple molecules

Ionic structures

High bp/mp

Low bp/mp

High bp/mp

Volatility

High bp/mp

Conduct in solid/liquid state

Non-conductor

Conduct in molten/aqueous state

Conductivity

Soluble only in polar solvent

Soluble only in organic non-polar solvent

Insoluble

Solubility

The amount of energy needed to remove one electron from a gaseous atom

ionisation energy

Subshell and electronic configuration

No. of orbitals

Type of subshell

1

3

5

7

s

p

d

f

Highest energy

• Each orbital can be filled by only 2 electrons, each with a different spin.
• Electrons go into different orbitals if given a choice.

5p

4d

5s

4p

3d

4s

3p

3s

2p

2s

1s

Lowest energy

solid (s)

liquid (l)

aqueous (aq)

gas (g)

chemical equations

y m b o l s

Solubility Table

Insoluble

Soluble

All nitrate salts

-1

chloride

bromide

iodide

hydoxide

nitrite/nitrate(III)

nitrate/nitrate(V)

hydrogensulfate

hydrogencarbonate

manganate(VII)/permanganate

-2

oxide

sulphide

sulphite/sulphate(IV)

sulphate/sulphate(VI)

chromate(VI)

dichromate(VI)

Monoatomic gases

helium

neon

argon

krypton

xenon

radon

lead(II) chloride & silver chloride

nitride

phosphate(V)

-3

Most chloride salts

t

a

t

e

Most sulfate salts

lead(II) sulfate, barium sulfate & calcium sulfate

diatomic gases

hydrogen

oxygen

nitrogen

chlorine

bromine

iodine

nitrogen monoxide

carbon monoxide

hydrogen chloride

+1

sodium

potassium

silver

hydrogen

copper(I)

ammonium

N

I

O

N

S

+2

magnesium

calcium

lead(II)

zinc

copper(II)

iron(II)

manganese(II)

+3

aluminium

iron(III)

chromium

Carbonates/Hydroxides of sodium, potassium & ammonium

Most other carbonates/hydroxides

A

T

I

O

N

S

triatomic gases

sulphur dioxode

nitrogen dioxide

carbon dioxide

ozone

dinitrogen oxode

acids

hydrochloric acid

nitric acid

sulphuric acid

sulphurous acid

carbonic acid

phosphoric(V) acid

ethanoic acid

others

sulphur trioxide

ammonia

methane

ethene