Question

$N{a_2}Se{O_4}$ and $N{a_2}S{O_4}$ show?
A. isomorphism
B. polymorphism
C. allotropism
D. ferromagnetism

Answer 1

The structural isomerism is a common term used for compounds having similar types of structures. The similarities between the compounds are more with minor differences.

Complete step by step answer:
The given two compounds are inorganic sodium salt. One is sodium sulphate and the other is sodium selenate. They have similar chemical formulas and only differ in the central atom one has sulphur atom in $N{a_2}S{O_4}$ and the other has selenium atom.
Sulphur and selenium are two elements in the periodic table with atomic numbers $16$ and $34$ respectively. They belong to the same group in the periodic table which is $16$. The group is called as chalcogens with the group elements oxygen ($O$ ), sulfur ($S$), selenium ($Se$), tellurium ($Te$), polonium ($Po$), and livermorium ($Lv$).
Let us check the two molecules for the given isomerism shown between them.
-Isomorphism. When two or more crystals which have identical chemical composition and they exist in the same crystalline form. They possess the same molecular formula and same molecular geometrical structure in crystal form. This property is referred to as isomorphism. So the given compounds $N{a_2}Se{O_4}$ and $N{a_2}S{O_4}$shows isomorphism.
-Polymorphism. It is the property shown by a certain substance which can exist in more than one crystalline form; the property is referred to as polymorphism. For example calcium carbonate is found to exist in two crystalline forms called calcite and aragonite. Thus the two compounds do not show polymorphism.
-Allotropism. It is also the property of the same substance which can exist in two different forms. The allotropes are known to have different chemical bonding between the bonded atoms. Thus the compounds do not show allotropism.
-Ferromagnetism. It is one type of magnetism property which is shown by the substances which form permanent magnets. They are attracted towards the magnets. The spin of electrons presents in these substances is in parallel spins. But in order to show magnetism property the central atoms must have unpaired electrons. Here sulphur and selenium atoms are in $+ 6$ oxidation state. Hence both have no unpaired electrons and cannot exhibit any kind of magnetism.
So, the correct answer is “Option A”.

Note:
Two substances must have the same chemical formulation for isomorphous crystals and must contain atoms which have similar chemical properties and the sizes. Thus the forces between molecules and ions are similar and have the same internal structure.