Naming Compounds
When a metal and a non metal join together the name of the metal
always comes first and the name of the non metal second.
The ending on the non metal changes to IDE:
e.g.
oxygen changes to oxide,
nitrogen changes to nitride.
Name these compounds:
1. Copper + oxygen
2. Iron + sulphur
3. Sodium + chlorine
4. Lithium + bromine
5. Potassium + iodine
6. CuS
7. AgBr
8. MgO
9. AlCl3
10. CaCl2
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Sometimes a metal is joined to a group of atoms (called a complex ion)
which contain a non metal combined with oxygen, the ending changes
to ATE:
e.g.
SO4 sulphur + oxygen = sulphate
NO3 nitrogen + oxygen = nitrate
CO3 carbon + oxygen = carbonate
Name these compounds:
1.
2.
3.
4.
Copper + sulphur + oxygen
Magnesium + nitrogen + oxygen
Zinc + carbon + oxygen
Potassium + chlorine + oxygen
5. Calcium + phosphorous + oxygen
6. NaNO3
7. CaCO3
8. AgNO3
9. KClO3
10. KMNO4
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To find the formula of an ionic compound
Things you need to know:
When a metal and a non metal join together they do so by ionic bonding.
The metal loses electron(s) to become a cation (positive ion).
The non metal gains electron(s) to become a negative ion (anion)
Step 1 - Look up the symbol for the elements involved on the periodic table:
e.g.
calcium chloride
calcium = Ca
chlorine = Cl
Step 2 - Look what group the element is in, decide how many electron(s) the element
gains/loses when it forms an ion and add the appropriate charge:
e.g.
calcium is in group 2 so loses 2 electrons to form the ion Ca2+
chlorine is in group 7 so gains 1 electron to form the ion Cl -
Step 3 - Do the charges balance? If not use the cross over method:
Ca 2+
Cl
-
This gives the formula CaCl2
You need two Cl- ions for every one Ca2+ ion so that the charges cancel out and the
compound is neutral overall.
Try these examples using the same method:
1.
2.
3.
4.
5.
Potassium iodide
Aluminium oxide
Magnesium bromide
Iron (III) chloride
Manganese (IV) oxide
Note: Some transition metals are able to form more than one ion.
e.g. copper can form Cu+ and Cu2+ ions.
The roman numerals in brackets in the name of the substance, tells you which of the
ions is used to make the compound.
e.g.
copper (II) sulphate contains the Cu2+ ion
copper (I) chloride contains the Cu+ ion
2
Writing word and symbol equations
Write a word and symbol equation for the reaction when magnesium
burns in air to produce a white ash of magnesium oxide.
Step 1 – Identify the reactants and the products in the question
Use a highlighter if you want.
Magnesium burns in air to produce a white ash of magnesium oxide
When something burns it only reacts with the oxygen in the air.
So in a combustion reaction the second reactant is always oxygen.
Step 2 – Write out the equation.
Put the reactants on the left hand side and the reactants on the right. Use an
arrow to show how the reactants change into the products.
Magnesium + oxygen → magnesium oxide
Reactants
Product
Step 3 – Use the periodic table to look up the symbols for the substances in the
reaction.
Remember only symbols for elements are found on the periodic table, so you
will have to work out the chemical formula of any compounds yourself.
magnesium = Mg
oxygen = O
Oxygen in the air exists as diatomic molecules, O2, so we use this in the
equation.
Magnesium forms Mg2+ ions and oxygen forms O2- ions. As the ions have the
same charge the formula for magnesium oxide will be MgO.
Step 4 – Replace the words with the symbols.
Mg + O2 → MgO
Step 5 – Balance the equation.
Are the numbers of atoms of each element the same on both sides of the
equation?
Mg
1
+
O2
2
→
MgO
1 1
No? Then you can change the number of atoms/molecules by adding a large
number in front of their formula. Never change the formula of compound.
2Mg +
2
O2
2
→
2MgO
2 2
3
Step 6 – Add state symbols
(s) = solid
(l) = liquid
(g) = gas
(aq) = solution
Most acids and alkalis that we use in school are solutions.
All metals are solids (except mercury!)
All ionic substances are solid.
2Mg (s)
+
O2 (g)
→
2MgO (s)
Useful information:
Common acids and alkalis
Gases and Others
Hydrochloric acid HCl
Sulphuric acid H2SO4
Nitric acid
HNO3
Sodium hydroxide NaOH
Potassium hydroxide KOH
Ammonium hydroxide NH4OH
Carbon dioxide CO2
Sulphur dioxide SO2
Oxygen O2
Hydrogen H2
Chlorine Cl2
Ammonia NH3
Complex ions
Sulphate SO42Nitrate NO3Phosphate PO43Carbonate CO32Hydroxide OHAmmonium NH4+
Salts formed when acids react with
metals, alkalis and bases are named
after the acid used.
Hydrochloric acid produces chlorides
Nitric acid produces nitrates
Sulphuric acid produces sulphates
Acid + metal → salt + hydrogen
Acid + alkali (or base) → salt + water
Acid + carbonate → salt + water + carbon dioxide
When any fuel burns carbon dioxide and water are produced.
Try these for yourself:
1. Iron reacts with oxygen to produce iron (III) oxide.
2. Methane burns in air to produce carbon dioxide and water vapour.
3. Magnesium reacts with sulphuric acid to produce a solution of
magnesium sulphate and water.
4. Hydrochloric acid reacts with calcium carbonate to produce carbon
dioxide gas, calcium chloride solution and water.
5. Zinc displaces copper from a solution of copper (II) sulphate, copper
metal is produced and a colourless solution
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