Ion notation
The ion notation is a notation for ions in chemistry . It uses superscript charges to indicate whether it is a cation ( + ) or anion ( - ) in an ionic compound . It is used, among other things, for the reaction equations of ions. The formula of sodium chloride (table salt) NaCl does not show that sodium ions (Na + ) and chloride ions (Cl - ) are hidden behind it . In the formula unit of neutral salts, the charges of the ions involved cancel each other out and the formula unit therefore carries no charge (NaCl). The ion notation is used in polar solvents (e.g. in aqueous solutions), as the ions are predominantly dissociated .
With the ion notation , the formula units (NaCl, MgCl 2 , Al 2 O 3 , FeO, Cu 2 S, CaSO 4 , Na 2 CO 3 etc.) can now be broken down into the ions involved in the salt , as well as the ion ratio due to the charges of the Determine ions:
| Formula unit | Ion notation | Salt name | |
|---|---|---|---|
| Cation / s | Anion / s | ||
| NaCl | 1 Na + | 1 Cl - | Sodium chloride |
| MgCl 2 | 1 mg 2+ | 2 Cl - | Magnesium chloride |
| Al 2 O 3 | 2 Al 3+ | 3 O 2− | Alumina |
| Fe (OH) 2 | 1 Fe 2+ | 2 OH - | Iron (II) hydroxide |
| Fe 2 O 3 | 2 Fe 3+ | 3 O 2− | Iron (III) oxide |
| Na 2 CO 3 | 2 Na + | 1 CO 3 2− | sodium |
| Pb (SO 4 ) 2 | 1 Pb 4+ | 2 SO 4 2− | Lead (IV) sulfate |
With the help of the ion notation one can find out the formula unit via the ion ratio and name the salt correctly. For many reaction equations in which salts are involved, it makes sense to use the ion notation.
Production of salts from the elementary substances, e.g. sodium chloride (table salt):
- 2 Na (s) + Cl 2 (g) → 2 NaCl (s) = 2 Na + +2 Cl -
- Sodium and chlorine gas react to form sodium chloride
Process of dissolving salts in water, e.g. sodium chloride:
- NaCl (s) → NaCl (aq) = Na + (aq) + Cl - (aq)
- Solid salt is converted into dissolved salt, dissolved ions are formed
In some cases, mixed forms of the ion notation are also used in the literature, whereby the charges are inserted in the salt formula : NaCl becomes Na + Cl - or MgCl 2 becomes Mg 2+ Cl 2 -
For didactic reasons, this approach should be avoided in school lessons, since the charges in the formula unit disappear or cancel each other out.
Individual evidence
- ↑ Volkher Biese, Uwe Bleyer, Manfred Bosse: Chemistry. Springer-Verlag, 2013, ISBN 978-3-322-91913-7 , p. 90.
- ^ Roland Benedix: Construction chemistry. Springer-Verlag, 2015, ISBN 978-3-658-04144-1 , p. 222.
- ^ Gisela Boeck: Short textbook chemistry. Georg Thieme Verlag, 2011, ISBN 978-3-131-67612-2 , p. 14.