Ionic compounds have higher melting points when their constituent ions have greater charges. Knowing
this, which compound has the highest melting point?
a) Potassium chloride
b) Sodium chloride
c) Magnesium chloride
d) Magnesium oxide

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.

14,16 18 reacts with group

the earth would become to overheated and everything alive on it will eventually die from overheating. plants will eventually die as well, water will evaporate, and it will be nothing but a hot planet without anything living on it.