EVERYDAY SCIENCE

Detailed explanation-1: -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-2: -The number of electrons in the outermost shell of a particular atom determines its reactivity, or tendency to form chemical bonds with other atoms. This outermost shell is known as the valence shell, and the electrons found in it are called valence electrons.

Detailed explanation-3: -In a chemical reaction the electron in the outer shell is lost. The reactivity increases as you go down the group because: The outer electron is further away from the nucleus with each additional electron shell making the force of attraction weaker. This makes it easier for an atom to lose it’s outer electron.

Detailed explanation-4: -Valence electrons are the outer-shell electrons of an atom. Valence electrons determine the reactivity of an atom.

Detailed explanation-5: -There is also an increase in electron density which makes the atom more reactive. Hence, reactivity increases from moving across a period.