Answer:
20.191 a.m.u
Explanation:
To calculate the average atomic mass for neon, we take into consideration the individual isotopes and their masses. We multiply the percentage of each of their abundances by their masses and add the results together to arrive at the value.
This can be done as follows;
[90.60/100 * 19.9924] + [0.26/100 * 20.9938] + [9.2/100 * 21.9914] = 18.113 + 0.055 + 2.023 = 20.191 a.m.u