Question

What is the compound in $MgS$?

Answer 1

Hint : We know that In order to check for the compound in $MgS$ firstly we have to solve the solubility of compounds, their covalent character needs to be checked. The compound which has the maximum covalent character will be classified as the least soluble, and vice versa.

Complete Step By Step Answer:
To answer the question, we must have a clear idea about Fajan’s rule. Fajan’s rule gives us the conditions for which covalent character can rise. According to it, covalent character is achieved when the size of the cation is small and the size of the anion is large
Nothing$MgS$ is the compound. Any compound is a combination of two or more different elements. And naturally, $Mg$ must be different from $S.$ Of course, if the compound is $MgS$, which contains two atoms, there couldn't be any "sub-compounds" within this compound, even if that were a thing, because the only atomic-scale components smaller than a diatomic compound (besides what's in an atom) is an atom.
Additional Information: We know that sodium is an alkali metal and magnesium is an alkaline earth metal. As atomic size decreases along a period, so we can say that has a smaller size than. So, as cation needs to be small, we cannot have sodium in the cation.

Note :
Remember that compounds which are ionic, or have polarity are soluble in water. However, there are some compounds which have differing polarity, which gets cancelled out and hence they are not soluble. Even though non-polar compounds are not soluble in water, they are soluble in substances like fats and oils.