Reactivity of Elements

In every group of periodic table reactivity of elements either increases or decreases from top to bottom. In case of metal reactivity increases from top to bottom and that decreases in case of non metals. The reactivity of element depend upon two major factors

• The number of electrons in outermost orbit
• Radius of atom

Reactivity of metals: In general reactivity of metallic element increases from top to bottom in the group of periodic table. As we move from top to bottom radius of atom increases and hence probability of losing electron from outermost orbit also increases as the distance of free electron from nucleus become high and electrostatic force between nucleus and the free electron becomes weak.
Q. Why potassium is more reactive than sodium?
Ans: As potassium is larger than sodium, potassium's valence electron is at a greater distance from the attractive nucleus and is so removed more easily than sodium's valence electron. As it is removed more easily, it requires less energy, and can be said to be more reactive.
Reactivity of non-metals: In case of metal it is most reactive if it has valence electron 1 or valency 1 but in case of non metal most reactive one is that which has number valence electrons 7 and valency 1. Unlike in case of metal, reactivity of non metal in a group as we move from top to bottom. The cause same as explained above but opposite with radius of atom. As we move from top to bottom in a group atomic radius increases and capacity of pulling external electron dcreases.

Q. Why is fluorine more reactive than chlorine?
Ans: This is because the valence/bonding electrons are closer to the nucleus in Fluorine than they are Chlorine and others and thus more strongly attracted. Fluorine is most electronegative, thus it is most reactive.