GENERAL KNOWLEDGE

Detailed explanation-1: -Hint: The outermost shell of the atom is known as the valence shell. The electrons which are present in the outermost shell of the atom are known as the valence electrons. They tend to determine the reactivity of the atom and also determine its tendency to form the chemical bonds.

Detailed explanation-2: -Relationship with Chemical Reactivity The chemical reactivity of an atom is mainly determined by valence electrons. Atoms which have a complete shell of valence electrons tend to be chemically inert. Atoms with one or two valence electrons are highly reactive.

Detailed explanation-3: -The number of electrons in the outermost shell of an atom determines its reactivity. Noble gases have low reactivity because they have full electron shells. Halogens are highly reactive because they readily gain an electron to fill their outermost shell.

Detailed explanation-4: -The number of valence electrons in one atom of each element is easily determined based on its position in the periodic table. For the main group elements (groups designated with a Roman numeral followed by the letter A), the number of valence electrons is equal to the Roman numeral.

Detailed explanation-5: -An atom with one or two valence electrons more than a closed shell is highly reactive, because the extra valence electrons are easily removed to form a positive ion.