what is the formula for iron(II) chloride?

Answer 1

Iron(II) chloride means that the iron ion is Fe2+ not Fe3+ so the correct formula to give this ionic compound a net charge of 0 is FeCl2 The 2 on the chloride (Cl) is subscripted (written below level of Cl

Iron is a transition metal, meaning it can have more than one valence state or charge. Not all transition metals have more than one valence state (silver ion is always Ag+ for example) but if an ion does have more than one valence, it will be a transition metal (look in the d-block of the periodic table to find it). That's the center portion of the chart that dips down to the 3rd row.