Valence Electrons

The electrons at the outermost shell of an atom are called valence electrons. They determine the reactivity of an atom and how they can bond with other atoms. An atom having 8 valence electrons is called stable atom and will not react or bond with other atoms.

VALENCE ELECTRONS

        The exceptions to the rules are Hydrogen (H) and Helium (He). Hydrogen atom has only one proton and one electron as shown in the following figure. Hydrogen atoms are highly reactive. Two hydrogen atoms bond with one oxygen atom and forms a molecule H₂0 called water.

HYDROGEN ATOM

        Helium is a noble gas even though it has two electrons and two protons as shown below.

HELIUM ATOM

        Atoms of Silicon (Si) and Germanium (Ge) have 4 valence electrons. These elements are used for manufacturing transistors.

SILICON ATOM

GERMANIUM ATOM