Working out the charges of ions
The An imbalance of electrons and protons in a material. An excess of electrons results in negative charge, a deficit of electrons results in positive charge. of many Electrically charged particle, formed when an atom or molecule gains or loses electrons. can be worked out using patterns in the A tabular representation of all known elements in order based on atomic number, eg all the noble gases are found on the right of the periodic table.. A substance made of one type of atom only. in the same A vertical column in the periodic table containing elements with similar chemical properties. form ions with the same charge.
A metal that is located in between group 2 and group 3 (labelled as group 13 on some modern periodic tables) and has brightly coloured compounds. (in the central block between groups 2 and 3) can have ions with different charges. The number in the name of the A substance formed by the chemical union of two or more elements. shows the charge of the metal ions in that compound.
For example, copper(II) sulfate contains Cu2+ ions.
The table shows the A combination of symbols that indicates the chemical composition of a substance. of some common transition metal ions.
| Metal ion | Formula |
| Silver(I) | Ag+ |
| Copper(II) | Cu2+ |
| Lead(II) | Pb2+ |
| Iron(II) | Fe2+ |
| Iron(III) | Fe3+ |
| Metal ion | Silver(I) |
|---|---|
| Formula | Ag+ |
| Metal ion | Copper(II) |
|---|---|
| Formula | Cu2+ |
| Metal ion | Lead(II) |
|---|---|
| Formula | Pb2+ |
| Metal ion | Iron(II) |
|---|---|
| Formula | Fe2+ |
| Metal ion | Iron(III) |
|---|---|
| Formula | Fe3+ |
Charged particle consisting of two or more atoms joined together. are formed from groups of The smallest part of an element that can exist.. The table shows the names and formulae of some of these ions.
| Cations (positively charged) | Anions (negatively charged) |
| Ammonium NH4+ | Hydroxide OH- |
| Nitrate NO3- | |
| Carbonate CO32- | |
| Sulfate SO42- |
| Cations (positively charged) | Ammonium NH4+ |
|---|---|
| Anions (negatively charged) | Hydroxide OH- |
| Cations (positively charged) | |
|---|---|
| Anions (negatively charged) | Nitrate NO3- |
| Cations (positively charged) | |
|---|---|
| Anions (negatively charged) | Carbonate CO32- |
| Cations (positively charged) | |
|---|---|
| Anions (negatively charged) | Sulfate SO42- |
The formulae of compounds containing polyatomic ions are worked out in a similar way to single atom ions. If more than one polyatomic ion is needed, its formula is written inside brackets.
Example
Calcium hydroxide contains Ca2+ and OH- ions:
- this is two positive charges and one negative charge
- to balance it will need, one Ca2+ ion and two OH- ions,
- so its formula is Ca(OH)2
Question
Deduce the formula for sodium carbonate.
Sodium carbonate contains Na+ and CO32- ions:
- this is one positive charge and two negative charges
- to balance, two Na+ ions and one CO32- ions are needed
- so the formula is Na2CO3
Question
Deduce the formula for lead(II) nitrate.
Lead nitrate contains Pb2+ and NO3- ions:
- this is two positive charges and one negative charge
- to balance it will need, one Pb2+ ion and two NO3- ions,
- so the formula is Pb(NO3)2
Naming ionic compounds with -ide and -ate
The name of an An ionic compound occurs when a negative ion (an atom that has gained an electron) joins with a positive ion (an atom that has lost an electron). ends in:
- -ide if it contains just two elements
- -ate if it contains three or more elements, one of which is oxygen
| Name (-ide) | Formula | Name (-ate) | Formula |
| Calcium carbide | CaC2 | Calcium carbonate | CaCO3 |
| Potassium iodide | KI | Potassium iodate | KIO3 |
| Iron(II) sulfide | FeS | Iron(II) sulfate | FeSO4 |
| Name (-ide) | Calcium carbide |
|---|---|
| Formula | CaC2 |
| Name (-ate) | Calcium carbonate |
| Formula | CaCO3 |
| Name (-ide) | Potassium iodide |
|---|---|
| Formula | KI |
| Name (-ate) | Potassium iodate |
| Formula | KIO3 |
| Name (-ide) | Iron(II) sulfide |
|---|---|
| Formula | FeS |
| Name (-ate) | Iron(II) sulfate |
| Formula | FeSO4 |