An atom’s electrons are distributed in an area or region around the nucleus. This region has energy levels that form orbits, which are represented by letters or numbers. Thus, the number of electrons present in the most extreme orbit is known as the valence electrons. Table of Values
The most extreme orbit is in turn called the valence orbit.
Eight is the maximum number of electrons that can settle in the most extreme orbit. Because of this, elements with an extreme and fully complete orbit are said to have an octet configuration.
This type of element does not easily combine with the others, consequently, there is little reactivity
In other words, its ability to combine is practically nil.
Elements whose valence orbit is incomplete have a tendency to complete their octet configuration and end up combining with atoms of the same or different types. Thus, valence is the ability of an atom to combine with another atom. Table of Values
The number of valences indicates the possibilities of an atom to combine with another when constituting a compound. This measure is related to the amount of chemical bonds established by the atoms of an element of a certain category .
There are several types or modalities of valences
Fixed ones have only one way to combine and all their states are positive (some of the elements with this characteristic are: lithium, sodium, potassium, silver, magnesium and zinc).
There are also fixed valences of nonmetals (for example, in hydrogen, fluorine or oxygen) and variable valences of metals. Table of Values
Anyway, all these characteristics are organized through tables that group the different chemical elements .
An illustrative example related to the ability to combine chemical elements
Elements combine with other elements in several ways: losing, getting, or sharing their electrons. For example, the electron configuration of sodium (Na) is 2, 8, 1 and that of chlorine (Cl) is 2, 8, 7, therefore, for sodium it is simpler to lose an electron than to gain seven electrons to complete its octet (on the other hand, chlorine easily accepts an electron to complete its octet rather than losing seven electrons). Table of Values
In other words, both sodium and chlorine have a valence of 1, as their combining ability is 1.