Question

What is the chemical formula for Magnesium sulphate?
A: $MgS{O_4}$
B: $Mg{\left( {S{O_4}} \right)_2}$
C: $M{g_2}{\left( {S{O_4}} \right)_2}$
D: $Mg{\left( {S{O_4}} \right)_3}$

Answer 1

Hint : Magnesium sulphate is a colourless crystalline substance that is prepared by the reaction of magnesium hydroxide and sulphur dioxide in the presence of air. It is basically an inorganic salt or a chemical compound consisting of the magnesium, sulphur and oxygen.

Complete Step By Step Answer:
As the name suggests, the given compound magnesium sulphate comprises a metal magnesium and a group of nonmetals sulphate. We know that any compound containing a metal and a non-metal is considered to be an ionic compound. In ionic compounds, we have to take into account the charges of each of the elements present in the compound. Now let us identify the formula for the given compound i.e. magnesium sulphate. Magnesium sulphate possesses a polyatomic ion (i.e. group of nonmetals (sulphate in this case) after the metal) so we'll use a table of names for the common polyatomic ions, along with the Periodic Table. Rules to write formula of a ternary ionic compound are listed below:
1. Using the periodic table, write down the symbol for the metal along with its charge.
In the present case, the symbol of metal Magnesium is $Mg$ having a charge +2.
2. Using the Common ion table, identify the symbol as well as charge of the polyatomic ion.
In the present case, polyatomic ion sulphate is written as $S{O_4}$ having a charge -2.
3. Check if the charges are balanced
In the present case it becomes $M{g^{2 + }}SO_4^{2 - }$ . The charges are balanced as summation of charges is zero i.e. $( + 2) + ( - 2) = 0$
4. If unbalanced charges are there, add subscripts such that net charge for the compound is zero.
In the present case, this step is not required as the net charge is already zero.
Hence, the chemical formula for magnesium sulphate is $MgS{O_4}$ .
Thus, the correct answer is Option A.

Note :
While writing the chemical formula of an ionic compound, never write the subscript '1'. And it should be noted that we can also have two polyatomic ions like $N{H_4}N{O_3}$ in the same compound. In this case, we have to find and write both of the names as identified from the Common Ion Table.