In this case, since, when we see an ionic binary salt like that formed by magnesium (metal) and fluorine (nonmetal), in order to set up the correct molecular formula we need to check out the periodic table in order to identify the suitable oxidation states, since metals remain positively charged as they lose electrons and nonmetals negatively charged as they gain electrons.
In such a way, since the oxidation state of magnesium is +2 and that of fluorine is -1 we write:
Next, we need to exchange the oxidation states as subscripts without the charge to obtain:
Which is the corrected molecular formula for magnesium fluoride.
The correct answer is c. Temperature is the average kinetic energy of a sample so if two samples have the same temperature they will also have the same average kinetic energy. I hope this helps. Let me know if anything is unclear.
One of the properties of metals is their abilities to form a stable compounds by losing electron(s). Metals form positive ions (cations) when they lose electron(s).