Answer:
See the answer below , please.
Explanation:
In a decomposition reaction, a certain compound is "broken" to give two or more different products.
An example for compound AB, giving as products A and B:
AB -> A + B
In the case of water:
2H20 -> 2H2 + 02, water decomposes giving Hydrogen and Oxygen
The factor in determining the average atomic mass of an element is:
B or 2 relative abundance of each isotope because the by looking at how many protons , electrons and neutrons the most isotope is of the element has relative abundance.