This work reports ab initio calculations for the alkali-dihydrogen reactions, A(+) + H-2 --> AH + H (with A = Li, Na, K), compared with the reaction, Li + F-2 --> LiF + F. The electron transfers in those two types of reaction are proved to be entirely different. While the electron donation from the metal atom to the halogen molecule in the lithium-difluorine reaction occurs suddenly at a long intermolecular distance, the. electron population is transferred progressively from the metal atom to the hydrogen molecule as the intermolecular distance decreases. We conclude that the harpooning model does not apply to the alkali-dihydrogen reactions. (C) 2002 Published by Elsevier Science B.V.