Answer
The atomic number is the total number of electrons. The valence electrons are only those in the outer shell.
The number of valence electrons is important to scientists because they participate in the formation of a chemical bond
Step-by-step explanation
The total number of electrons is equivalent to the atomic number of a neutral element. The total number of electrons must be equal to the total number of protons in the nucleus of a neutral element. The total number of electrons in an atom are classified into two namely; core electrons and valence electrons.
The core electrons are those occupying the innermost shell or lowest energy levels while the number of valence electrons is the electrons occupying the outermost shell or highest energy level of an atom.
The number of valence electrons is important to scientists because they participate in the formation of a chemical bond; in a single covalent bond, both atoms in the bond contribute one valence electron in order to form a shared pair. The presence of valence electrons can determine the element's chemical properties and whether it may bond with other elements: For the main group element, a valence electron can only be in the outermost electron shell.