A valence electron is a type of electron present in an atom that works to aid in the process of chemical bond formation with other atoms. These electrons are present in the outer shell of an atom.
During a chemical reaction, the valence electrons on an atom may be lost or gained. This type of electron aids in determining whether an element bonds with another element and the chemical properties that an element has. These electrons are on the outermost shell in a main group element. They may also occur on the inner shell of a transition metal, such as copper, iron, chromium and manganese.
To determine how many valence electrons are present, scientists should look at the vertical column, which is the periodic table group, where the element is. How many valence electrons an element has is the group number's units digit. The exception to this is with the transition metals in groups three through 12. When it comes to main group elements, the electron configuration helps to determine the number of valence electrons, but this is not true for transition metals. This is because these metals have no subshells that are incomplete and the energy is generally close to an (n+1) electron.