The question on my homework was "Neon has 3 isotopes with the masses of 20 21 and 22. What is the mass, in grams of a proton?" My teacher never went over this in class and the the way the textbook tries to explain it is terrible and I'm just really confused.

Thank you for the opportunity to help you with your question!

Ne – 20, Ne – 21 and Ne – 22 in percentage is - Ne -20 = 90.92% , Ne – 21 = 0.26% and Ne – 22 = 8.82 %.

So, if the percentage of the isotopes is known, the average atomic mass of an element can be calculated.

To calculate the average atomic mass of an isotope, the percentage of all isotopes are taken, and divided by the sum of masses of both isotopes.

Example: Calculate the atomic mass of chlorine from the following data: Cl : 37 = 24.6 % , Cl : 35 = 75.4 %.Average atomic mass of chlorine = 75.4×35+24.6×3775.4+24.6 = 35.492.

Thus, the average atomic mass of chlorine from this data is 35.492 amu.

Please let me know if you need any clarification. I'm always happy to answer your questions.

Oct 21st, 2015

FOR NEON

The average atomic mass of neon is the weighted average of the mass of the isotopes and equal to 20*0.9092 + 21*0.0025 + 22*0.0883 = 20.10