2. Comparing Atomic Mass and Mass Numbers Atomic Mass Mass Number The mass number is the total amount of protons and neutrons in an atom. An atom of an element can have different mass numbers due to unbalanced atoms called isotopes. Average weight of all balanced atoms and all isotopes of an element based on how likely they are to appear. The atomic mass is an average weight of all known balanced atoms and isotopes. Average weight of all balanced atoms and all isotopes of an element based on how likely they are to appear. Weight of an individual atom or isotope of an element

3. mass numberexact weightpercent abundance 12 C12.000000.9890 13 C13.0033550.010 1.Take each isotope of an atom and multiply its exact weight by its percent abundance. 2.Add together to get the atomic mass. This is the solution for carbon: (12.000000) (0.9890) + (13.003355) (0.0110) = 12.011 amu 11.868.143036905 11.868.143036905 12.011036905

4. mass numberexact weightpercent abundance 1414.003074.9963 1515.000108.0037 Problem #2: Nitrogen This is the solution for nitrogen:

5. Activity Find your fellow isotopes Determine your mass number Determine your abundance percentage (number in group/total number of atoms) Share your information with other groups Calculate your atomic mass

6. 1) Rubidium has two common isotopes, 85Rb and 87Rb. If the abundance of 85Rb is 72.2% and the abundance of 87Rb is 27.8%, what is the average atomic mass of rubidium?

7. 2) Uranium has three common isotopes. If the abundance of 234U is 0.01%, the abundance of 235U is 0.71%, and the abundance of 238U is 99.28%, what is the average atomic mass of uranium?

8. 3) Titanium has five common isotopes: 46Ti (8.0%), 47Ti (7.8%), 48Ti (73.4%), 49Ti (5.5%), 50Ti (5.3%). What is the average atomic mass of titanium?

9. Naturally occurring chlorine that is put in pools is 75.53 percent 35Cl and 24.47 percent 37Cl Calculate the average atomic mass.

10. Magnesium consists of three naturally occurring isotopes. The percent abundance of these isotopes is as follows: 24Mg (78.70%), 25Mg (10.13%), and 26Mg (11.7%). The average atomic mass of the three isotopes is 24.3050 amu.