What Are Valence Electrons
Valence electrons are the electrons present in the outermost shell of the atom. These are the electrons that play a significant role in determining the reactivity of the particular element. The reason for this can be given to lie in the fact that valence electrons are the ones that take part in formation of chemical bonds with atoms of other elements. Usually, the number of valence electrons of an element is referred to as the valency of the element. In certain kind of elements referred to as ‘transition elements’, some of the electrons in the penultimate shell also involve in bond formation along with the electrons of the outermost cell and thus, they too are referred to as valence electrons.
The number of valence electrons in an element can be easily found out if one knows the position of the element in the periodic table. However, as mentioned, transition metals are more complex and determination of their valency makes use of different rules. The connection between the number of valence electrons in an element and its reactivity can be explained as mentioned below. An element that has a closed shell is chemically inert as it has the most stable configuration that an element with the particular atomic number needs to have.
On the other hand, an element that has a few electrons more than the closed shell configuration of the lower shell, tries to lose out the valence electrons and gain stability. Sodium is an element with 1 valence electron which is lost to attain stability. A similar explanation can be given to the behavior of the elements that have a few atoms required to attain a closed cell configuration. The only difference is that they try to attract atoms from other elements to reach this state. Halogens like chlorine, bromine etc have 5 valence electrons and attract the extra 1 electron from other elements to attain the ideal configuration. The tendency to lose an electron is termed as ‘electropositive nature’ and this is a characteristic of the metals while the tendency to attain an electron is termed as ‘electronegativity’ and non metals generally exhibit this characteristic.
Thus, it goes without saying that various chemical properties of the elements greatly depend on the number of valence electrons in them. Metals which generally have one or two valence electrons are the best electrical conductors owing to the fact that they tend to lose out the extra electron in them, thereby, having a free positive ion that can provide a medium for the easy conduction of electricity in the metal.