Elemental exonium (not a real element) consists of two major isotopes abundance mass 18% 98 amu 82% 112 amu what is the atomic weight for exonium? answer in units of amu

In general chemistry, isotopes are a group of substances that belong to the same element. An element is characterized in the periodic table by their atomic number, which is the number of protons in an atom. Therefore, these substances have the same atomic numbers, but differ in mass numbers. Mass number is the sum of the number of protons and neutrons in the nucleus of an atom. 

To determine the atomic weight of an element, you take the average weight of all the existent isotopes of that said element. The calculation would require to multiply the exact mass of the isotope to its abundance. Then, sum them all up.

Atomic weight = 98(0.18) + 112(0.82)
Atomic weight = 109.48 amu

A.(nh4)(2co3)is the correct answer 

They make up examples of physical properties