Key difference - valence vs. valence electrons
Although the two terms valence and valence electrons are very closely related, there are subtle differences between the two. 'Valence', after its literary meaning in chemistry, refers to capacity. Chemically speaking, the valency of an element is the number of bonds it can form. The valence electrons would be the electrons that are available for this bond. Therefore, the main difference between valence and valence electrons is that valence is the number of bonds that can be formed by an atom or element, while valence electrons are the electrons that participate in that bond formation.
What is valence?
According to the IUPAC definition, valence is “the maximum number of monovalent atoms (originally hydrogen or chlorine atoms) that can combine with an atom of the element under consideration or with a fragment, or for which an atom of this element can be replaced”. It is important to note that monovalent atoms are being considered here, as they would each pair with an electron. However, when an element such as oxygen, which is a divalent atom, is used for this purpose, the valence is equal to twice the amount of oxygen that was involved in the formation of bonds.
A valence diagram of a compound would show the connectivity of atoms in lines, and this would not necessarily represent a pair of shared electrons. It was the concept of valence that gave rise to modern theories about chemical bonds such as: Valence bond theory, Lewis structures, molecular orbital theory and valence shell electron pair repulsion theory. The main group elements usually have a valence, while the transition metals are known for their multiple valences.
What are valence electrons?
Valence electrons are the electrons that are involved in bond formation. They are usually in the outermost shell of main group elements and can even be in the closed shells of transition metals because they have multiple valencies. It is also the valence electrons that define the chemical properties of each element, and they are grouped under the columns of the periodic table based on the number of valence electrons.
Atoms that have one or two more valence electrons than is required to form a noble gas (inert) electron configuration are very reactive compared to atoms that have more valence electrons in the outer shell. For example, if an element has to give up its electrons in order to achieve the noble gas electron configuration, it is easier to remove an electron or two than to remove more electrons against nuclear attraction. The same applies when electrons have to be absorbed in order to achieve a noble gas configuration. In this case, under strong electronegative influences, it is easier to accept a few electrons than many. Since the valence electrons are in the outermost shell of an element, they can absorb energy photons and be excited to a higher energy level, and in a similar way can give off energy and sink to a lower energy level. During the oxidation, the electrons that absorb sufficient energy can be removed from the element due to the high kinetic energy.
Difference between valence and valence electrons
The valence of an atom / element is the number of bonds it can form around it.
Valence electrons are generally located in the outermost shell of the element and take part in the formation of chemical bonds.
Valence explains the formation of bonds between atoms.
Valence electrons are more associated with elemental character.
Valence is just a concept and does not involve electron transitions.
Valence electrons take an active part in the formation of bonds and the formation of atomic ions through their transition chemistry.
Effect on transition metal elements
Transition metals can have several valencies depending on the element.
The number of valence electrons in a transition metal is expressed at the time of observation because each state of the element has a certain number of valence electrons.