Question

In the reaction $Mg+O_2\to 2MgO$ the atomicity of MgO is:
A. One
B. Two
C. Four
D. None of these

Answer 1

Hint: A molecule is a substance made up of various atoms. The atomicity of any compound is defined as the number of atoms present in that compound. So, atomicity can lead to the identification of the types of molecules as monatomic, diatomic, triatomic, or polyatomic. Atomicity is expressed in numbers.

Complete answer:
We have been given a reaction in which magnesium reacts with oxygen gas to form magnesium oxide. We have to find the atomicity of magnesium oxide. As any molecule is made up of certain atoms, the number of atoms in that molecule tells us the atomicity of that molecule.
The product of magnesium and oxygen is MgO. This molecule contains magnesium and oxygen in a 1:1 ratio as both are in the same quantity which is 1, so the atomicity of this molecule is 1 Mg atom + 1 O atom that is equal to 2.
Therefore, in the reaction $Mg+O_2\to 2MgO$ the atomicity of MgO is two.

So the correct answer is option B.

Note:
The reaction given here is a type of combination reaction where two reactants react and combine to form a single molecule. The number of moles of magnesium oxide is 2. The number of moles does not count in the atomicity as they are the amount of the compound, while the number of atoms in the compound MgO is 2. This also means that the nature of this molecule is diatomic.