Chemistry help please???? (thanks!!!)?

Ca is a second period element, thus it forms a 2+ ion, Ca2+ to empty it's outer shell of electrons and expose a shell with a full octet . Iodine, and all the halides (F, Cl, Br) happily gains an electron to fill it's outer shell, resulting in a I- ion. Charge balance tells us the formula must be CaI2 (the 2 is a subscript) and the formula weight is 126 grams/mol, so you will have twice as many I- ions as Ca2+ ions, or 1.48x10^22 I- ions.