. F, Cl and br are the elements each having seven valence electrons
Which of these (i) has the largest atomic radius, (ii) is most reactive? Justify your answer stating reason for each.
Ans. F, Cl and Br belong to the same group (17th) as each has same number of valence elements'7'.
i. Out of F, Cl and. Br, Bromine has the largest atomic radius because on going down in a group of the periodic table, the size of atoms increases as number of electron shell of electrons is added to the atoms at every step.
ii. Out of F, Cl and Br, Fluorine is the most reactive because the chemical reactivity of non-metals decreases on going down in a group of the periodic table as moving down in a group of non-metals, the size of the atoms goes on increasing. Thus the nucleus of atoms goes more and more deep inside it and hence attraction for the incoming electron5 decreases. Therefore the tendency of atoms to gain electrons decreases, due to which their reactivity decreases.