Why does argon exist in nature as individual argon atoms and chlorine exist in nature as 2 chlorine atoms covalently bonded together ?

Argon has 8 valence electrons and no extras, it does not require a bond in order to fill its shells, its satisfied by itself.

Chlorine is missing 1 Electron, if it connects with another Chlorine it will be satisfying both of their needs with a Covalent bond.

Explanation:

1. for the first question, we must find the mass of the anhydrous salt, mgso₄. the molar mass for mgso₄·7h₂o is 246.47 g/mol, while that of mgso₄ is 120.37 g/mol.7.834 g mgso₄·7h₂o * 1 mol mgso₄·7h₂o/246.47 g * 1 mol mgso₄/1 mol mgso₄·7h₂o * 20.37 g mgso₄/mol = 0.647 g mgso₄

2. mass of water = mass of sample - mass of anhydrous salemass of water = 7.834 - 0.647 = 7.19 gpercent water in hydrate = 7.19/7.834 * 100 = 91.74%