Why potassium reacts more vigorously with water as compared to sodium?

4 Comments

1. Varaprasad says:

   March 2, 2010 at 4:59 PM

   potasium IP or IE is less than Na hence it is soluble in water more than sodium
2. Balik K says:

   March 2, 2010 at 4:59 PM

   As you know, Na is number 11 in the periodic table, whereas K is number 19. Thus, K is a larger atom than that of Na, although they are both in the same group on the table (alkali metals.)

   As the atoms become larger, their outer electrons are further from the nucleus, in terms of shells. Thus, the energy required to extract the outermost electron from the atom, when reacting or bonding, decreases.

   (The amount of energy required to extract the outermost electron is also called the first ionisation energy, so this can be put most simply as "Because the first ionisation energy decreases down a group.")

   Thus, Rb has a lower ionisation energy than K, because its electrons are further away from the nucleus, and less energy is required. K is more reactive than Na for the same reason.