How do you calculate the atomic mass of an element when an isotopic composition is given

99.985% 1H; 0.015% 2H
Please show steps to solve!

The idea is the sum of the parts is equal to the whole.

100*avgatomicmass= 99.985*1 + .015*2

solve for avgatomicmass.

How???

Bob please help further

divide both sides by 100.

then on the right, muliply the terms and add.

Can you please show how in long form so I know how to do it! Thanks

Help please see last entry

Can you please show how in long form so I know how to do it! Thanks

ANYONE!!!

Here is what Bob Pursley wrote.

100*avgatomicmass= 99.985*1 + .015*2

Here is a rewritten form of his equation although his instructions for solving the equation are simple.
100*x = [99.9985*1 + 0.015*2]
solve for x which is the average atomic mass.

To calculate the atomic mass of an element when an isotopic composition is given, you need to consider the isotopes present in the element and their respective atomic masses. The atomic mass is calculated by multiplying the atomic mass of each isotope by its relative abundance (given as a percentage), and then summing up these values.

Let's solve the example you provided, where the isotopic composition of hydrogen is given as 99.985% 1H and 0.015% 2H.

Step 1: Determine the atomic mass and relative abundance for each isotope.
- The atomic mass of 1H (hydrogen-1) is approximately 1.0078 amu (atomic mass units).
- The atomic mass of 2H (deuterium) is approximately 2.0141 amu.

Step 2: Calculate the contribution of each isotope to the atomic mass.
- For 1H: Multiply its atomic mass (1.0078 amu) by its relative abundance (99.985% or 0.99985) to get the contribution of 1H to the atomic mass: 1.0078 amu * 0.99985 = 1.0077 amu.
- For 2H: Multiply its atomic mass (2.0141 amu) by its relative abundance (0.015% or 0.00015) to get the contribution of 2H to the atomic mass: 2.0141 amu * 0.00015 = 0.0003 amu.

Step 3: Sum up the contributions of each isotope to obtain the atomic mass.
- Add the contribution of 1H (1.0077 amu) and the contribution of 2H (0.0003 amu): 1.0077 amu + 0.0003 amu = 1.008 amu.

Therefore, the atomic mass of hydrogen, considering the given isotopic composition, is approximately 1.008 amu.