Under which sphere should clouds should be classified?

How manyatoms of mercury are in 1.4214e+1 ml sample

Sally is making a model of a magnesium atom with an atomic mass number of 24 for her chemistry class. she has foam balls for the protons, neutrons, and electrons. she has added 6 neutrons to her model so far. how many more neutrons does she need to add to complete her neutral atom of magnesium?

If anyone would be able to me out with these three questions it would be these are from the chem 2202 course.