three isotopes of hydrogen occur in nature. calculate the average atomic mass of hydrogen to two decimal places, given the following relative atomic masses and abundances of each of the isotopes hydrogen-1, 99.985%, hydrogen-2,0.015% and hydrogen- 3,0.00037%

Question

Ferredoxin4 · Answer

I mean it's 1.008 but if you want the calculation:

Avg Atomic Mass = Σ(mass of isotope)(relative abundance)

(1)(0.99985)+(2)(0.00015)+(3)(0.0000037)

Xotchil · Answer

@Ferredoxin4 the calculations gave me 1.0001611
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Ferredoxin4 · Answer

Yeah that's fine, in the periodic table they'll put 1.008

Xotchil · Answer

Oh ok

Ferredoxin4 · Answer

See, your question didn't offer the most precise values for each isotope. It just gave the name of the isotope and we are forced to use their rounded Mass Number. But in reality, there's mass spectroscopy completed of a sample of hydrogen and it's plotted on a Mass spectra table and it's much more precise.

Therefore from your question, we only get about 1.00015. The 1.008 on the periodic table comes from more precise values of their isotopes.