COVALENT BONDING
When two non-metal atoms react together, they share electrons to fill their outershells so sharing is the ONLY way they can both gain.
e.g. hydrogen
Molecule – a group of atoms joined by covalent bonds.
On the left of an equation is the reactants and on the right is the products.
e.g. Reactants Products
Every element has a charge, depending on the charge the amount of atoms of each substance is decided e.g. in the reaction Magnesium (+2) and Fluorine (-) there must be twice as many fluorine’s as Magnesium’s to cancel each other out.
Symbols of State
(s) – solid
(l) – Liquid
(g) – Gas
(aq) – aqueous solution(dissolves in water)
IONS
Some ions contain more than one element e.g. NO3 (-) but the same rules apply as in simple ions. Brackets are needed when more complex ions are involves
e.g. Fe(3+) + NO3(-) Fe(NO3)3
elements tend to be positive ions and compounds negative ions.
ELEMENTS AND COMPOUNDS
If you have one metal and one non-metal the compound will end in “ide”.
e.g Magnesium + Oxygen Magnesium oxide
If you have two non-metals the compound will end in “ate”
e.g. Copper + sulphur Copper sulphate + Oxygen
The numbers in a formula show the amount of each kind of atom in the compound or element.
e.g. H2 two hydrogen atoms
BALANCING EQUATIONS
- Chemical reactions are really re-arrangements of atome reactant substances that have their atoms re-arranged and they become product substances. In the course of a chemical reaction atoms can NOT be created or destroyed.
Therefore the number of each substance on each side of an equation MUST be the same.
e.g. BaCl2 + Na2 SO4 BaSO4 + 2NaCL
Noble gases are in group 8/0
Noble gases- Helium – (He) used to fill air balloons
Neon – (Ne) forms a bright light when an electric current is passed through it.
Argon – (Ar) used to fill light bulbs
All noble gases are unreactive because they have full outer shells so do not need to lose or gain any electrons.
Alkali Metals are in group 1
Lithium (Li)
Sodium(Na)
Pottasium(K)
- When alkali metal atoms react they become posotive ions by losing elecetrons.
- Potassium is more reactive than Lithium and Sodium, it is lower down in the periodic table.
- Alkali metal compounds are white when solid an colourless in a solution, soluble, they have a PH above 7, i.e. alkali
Halogens are in group 7
Flourine Chlorine Bromine Iodine
yellow green red/brown Purple
gas gas solid liquid
Fl2 Cl2 Br2 I2
A Halide is formed when a Halogen is in an equation.
TRANSITIONAL METALS
- Found between groups 2 and 3
- Can form oxides with two different formulas both oxides formed are colourless
- Transitional metals and their compounds make good catalysts.
Uses:
Iron – man hole covers
Copper – water pipes
Nickel – coins
Titanium – aircraft industry
SODIUM CHLORIDE
Can be ontained from collecting sea water and allowing water to evaporate leaving salt.
Formula = Na + Cl NaCl
