Cobalt (I) fluoride
how do i write this into a formula?

The answer would be CoF for Cobalt (I) Fluoride.

Explanation:

So first of all you take your periodic table and look at the valence electrons of Fluorine...it is 1. You don't need to look the valence electron of Cobalt because the "I" after Cobalt tells its valence electrons (it is a transition metal that is why). Now that Cobalt has a +1 charge and Fluorine has a -1 charge, it is automatically nuclear (means charge are cancelled out to 0). Therfore the answer is CoF.

Hope it helps and mark as Brainliest if possible

the formula mass of a molecule or a compound is the sum of the atomic weights of the atoms in its empirical formula

(that's what i know about formula mass)