The relative abundance of indium-113 is 4%.
The isotopes are species of the same element having the same atomic number but a different mass number.
The elements occurring in nature exist as multiple isotopes.
When we take into account the existence of these isotopes and their relative abundance (percent), the average atomic mass of that element can be computed, which is given by the following formula,
Average atomic Mass= (%age of isotope 1) x (Mass of isotope 1) + (%age of isotope 2) x (Mass of isotope 2)/100
Indium exists in the form of Indium-113 and Indium-115.
The mass of Indium-113 is 112.90 u.
The mass of Indium-115 is 114.90 u.
The average atomic mass of Indium is 114.82 u.
Let the %age of isotope 1(Indium-113) be X.
Then, the %age of isotope 2(Indium-115) would be 100-X.
Applying the values in the formula,
Average atomic mass = 112.90X+114.90(100-X)
114.82 = 112.90X+114.90(100-X)
On solving the above equation, the value of X comes out to be 4%.
Thus, the relative abundance/%age abundance of Indium-113 is 4%.
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