Element X is a solid at room temperature. It needs one electron per atom to gain the electronic structure of a noble gas.
It is the least reactive element in its group.
What is the element X?

1.At
2.Cs
3. F
4. Li​

Consider the following reactions. (note: (s) = solid, (l) = liquid, and (g) = gas.) mg(s) + ½o2(g) → mgo(s) + 146 kcal/mole h2(g) + ½o2(g) → h2o(g), δh = -57.82 kcal/mole what type of reaction is represented by the previous two examples?