ATOMS, ELEMENTS AND COMPOUNDS
All substances are made from atoms.
Substances made of only one atom are called elements e.g. silver, gold, oxygen.
Most substances are made up of more than one atom, these are called compounds.
Every atom has a nucleus in the middle, surrounded by electrons.
NEUTRONS = mass number - atomic number
MASS NUMBER = protons + neutrons
PROTONS = atomic number (bottom number)
ELECTRONS = PROTONS
Protons = positive = +1
Neutrons = neutral = 0
Electrons = -1
ELECTRONS IN ATOMS
First shell = up to 2
Every other shell = up to 8
Group 0 of periodic table
All have 8 electrons in outermost shell
Limestone is made of calcium carbonate.
Calcium carbonate = CaCO3
When heated, calcium carbonate breaks down to make calcium oxide and carbon dioxide - thermal decomposition.
Testing for carbon dioxide =
calcium hydroxide + carbon dioxide --> calcium carbonate + water
(limewater) (precipitate - cloudy)
Ca(OH)2 + CO2 --> CaCO3 + H2O
LIMESTONE REACTION CYCLE
Displacement reaction = one metal is more reactive than the other.
e.g. magnesium + zinc oxide --> magnesium oxide + zinc (because magnesium is more reactive than zinc)
Smelting = heating a metal ore in order to extract its metal.
Bioleaching = using bacteria to extract copper.
Phytomining = using plants to produce pure copper.