genral chemistry revision

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The Atom

All the element are made of atoms which themselves are made up of these types of subatomc particles

Protron : + charge

Nuetron : nuetral

Electron : - charge

the proton and the nuetron exist in the middle of the atom in an area called the nucleus. the electron exists in the energy levels around the atom. The atom is hydrogen it has only one protron and one electron.

Helium is the next simplest, it has two protrons and two electrons.

Atomic Mass (number of protons + number of nuetrons)

Atomic Number (number of protons)

for a nuetral atom the number of electrons is the same as the number of protrons. if there are too many or too few electrons then it becomes an ion

the elctrons exsits in the energy levels were te first level can only hold 2 electrons, 2nd level can only hold 8 electrons, the 3rd level can 10 electrons

Oxidation

many chemical reactionas can be classed as oxidation reactions,

Gains Oxegen

Loses hydrogen

Gains electrons

Burring is a form of oxidation, when fuel burns is combines with oxygen and generates heat. Reactions that generate heat are called exothermic reactions

eg. burning magnesium

Magnesium burns in air with a very bright white flame

Magnesium + oxygen -> magnesium oxide

When things burn the requie 3 thing

Heat

Oxygen

Fuel

this is the fire triangle

to but out a fire you need to remove one of these things, eg. a fire blanket removes oxygen

If an oxidising agent is use in a fire it has its own supply of oxygen and is there fore difficult to put out

eg.fireworks

the most Common use of combustion by humans is the combustion of hydrocarbons

Rusting

rusting is a special type of oxidation reaction specific to iron or steel

Iron + orxygen + water -> hydrated iron oxide

Rust can be prevented by using a barrier of paint, plastic or oil. another method is to use small about of reactive metal (like zinc) this is call sacrificial protection

Copper

Reactive metels like copper dont exist on earth in there metalic state. they exist as compound called ores. these metal can be extracted in a procese called smelting eg-

copper + carbon oxide

heat

copper + carbon dioxide

this is a reduction reaction (opposite of oxidation)

Iron

iron can be smelted from iron ore in a simular way to copper. however this requires much more heat. air is blasted through a furnace: a blast furnace

iron oxide + carbon -> iron + carbon dioxide

Carbon + oxegen -> carbon dioxide

Carbon dioxide + carbon -> carbon dioxide

the atom

oxididiation

Copper, iron