How do I calculate the average atomic mass?

Question

I am a junior in high school taking advanced chemistry

Answer 1

The average atomic mass is found by taking the mass of each isotope of the element into consideration.

Multiply the mass of each isotope by the decimal form of the percent abundance of each isotope. You will get several answers--one for each isotope. Add all of these answers together and you have the average atomic mass for all of the isotope of the element.

Answer 2

Your question is unclear. Maybe you want to calculate the average atomic mass of chlorine, given that there are two isotopes of chlorine, Cl-35 and Cl-37, and that Cl-37 is only about 25% of the natural abundance of chlorine, and that Cl-35 is 75%. So then you have to come up with the result that the atomic weight (average atomic mass in nature) of chlorine is 35.457. Congratulations on making it into advanced chemistry at a young age. Come back here often, and come to TheChemistryCluster in Yahoo groups.

Answer 3

atomic mass is calculated by adding up the number of protons and neutrons in an atom.

to work out the average atomic mass of a compound containing more than one type of atom, you first have to know the ratios or percentage of each type of atom in the compound, you then for each type of atom present find the atomic mass of it, divide by 100 and multiply by the percentage of compound that consists of this atom. you do this for each atom present and add up the values.

for example

i have a compound with 20% hydrogen, and 80% helium (keepin it simple so using small elements, and we also need to ignore the fact that they are gasses ideally). H's atomic mass is 1 and being present in 20% of this compound, i get (1 / 100) x 20, which is 0.2, and with helium i use 4 / 100 x 80, which gives 3.2.

0.2 + 3.2 gives 3.4 which i believe would be your average atomic mass of this compound.

Answer 4

atomic massesa re already calculated for all known elements, did you discover a new element?