May 06, 2021, 01:00:15 PM
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Topic: Why is the atomic weight of oxygen less than 16 when its isotopes are 16,17,18?  (Read 4022 times)

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Offline gracie7

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I cannot figure out why the atomic wt. for oxygen is less than 16 (i.e., 15.999), when its three main, stable isotopes have weights of 16, 17, and 18. Can anyone please explain this to me?

Offline JGK

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Naturally occurring oxygen is composed of three stable isotopes, 16O, 17O, and 18O, with 16O being the most abundant (99.762% natural abundance).

I would say it's due to rounding up of the actual weights rather than reporting to a load of decimal places for each isotope.
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Online Borek

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What is EXACT mass of 16O?

Hint: it is not 16.
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Offline AWK

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