Based on this, you can tell that Iron(Fe) does not react with Nitrogen(N), but does with something in normal air. The element the Iron is reacting with Oxygen(O), and the compound that is formed is called iron oxide.
Let the charges be q and Q separated by a distance r. The electrostatic force , F = kqQ/r² = 72 units. If q = 2q and Q = 3Q, then the new electrostatic force is
