Question

a) Explain the Law of multiple proportions with help of an example. [2 marks]

b)Atomic number of an element is 16 and the mass number is 32
i) Find the number of protons, electrons and neutrons in the atom. [1 Mark]
ii) Write the electronic configuration of the atom. [1 Mark]

Answer 1

a) Law of multiple proportions states that when two elements A and B combine together to form more than one compound, then different masses of A which separately combine with a fixed mass of B are in simple ratio.

Carbon combines with oxygen to form two different oxides, carbon monoxide $CO$ and carbon dioxide ($C{O}_2$. The ratio of masses of oxygen in $CO$ and ($C{O}_2$ for fixed mass of carbon is 1: 2. [2 marks]

b)
i) Atomic number = 16
Mass number = 32
We know that atomic number is equal to number of proton and number of proton is equal to the number of electron.
So, Proton number = electron number = 16.
We also know that,
Mass number = number of neutrons + number of proton
32 = X + 16 ( X= number of neutron)
X=16 [1 Mark]

ii) The electronic configuration of the element is 2, 8, 6.
[1 Mark]