Valence electron
In chemistry, valence electrons (often also called outer electrons ) are the electrons that are located in the outermost atomic orbitals and can participate in bonds (" valences ") between atoms .
In the main groups - elements which are the electrons of the outermost shell ( valence ) in the s- and p-orbitals, wherein the transition metals are formed on the outermost shell and in addition, the electrons in the d orbital of the preceding shell.
If valence electrons are involved in bonds, they are also binding electrons . But they can also be non-binding and are then not binding electrons. This means that the number of valence electrons does not always match the number of electrons actually involved in bonds, depending on the chemical state of the corresponding atom.
| Group on the periodic table | Number of valence electrons |
|---|---|
| Group 1 (I) ( hydrogen and alkali metals ) | 1 |
| Group 2 (II) ( alkaline earth metals ) | 2 |
| Group 13 (III) (boron group) | 3 |
| Group 14 (IV) (carbon group) | 4th |
| Group 15 (V) (nitrogen group) | 5 |
| Group 16 (VI) ( chalcogens ) | 6th |
| Group 17 (VII) ( halogens ) | 7th |
| Group 18 (VIII or 0) ( noble gases ) | 8 (exception He : 2) |
For example, B. the element chlorine has seven valence electrons, all of which are involved in bonds in the perchloric acid (HClO 4 ) molecule . In contrast, in hydrogen chloride (HCl) only one of the seven electrons is involved in the electron pair bond.
