November 23, 2024, 03:26:28 PM
Forum Rules: Read This Before Posting


« previous next »
Pages: [1]   Go Down

Topic: Why is the atomic weight of oxygen less than 16 when its isotopes are 16,17,18?  (Read 4712 times)

0 Members and 1 Guest are viewing this topic.

Offline gracie7

  • Very New Member
  • *
  • Posts: 1
  • Mole Snacks: +0/-0
Why is the atomic weight of oxygen less than 16 when its isotopes are 16,17,18?
« on: December 18, 2009, 11:33:26 AM »
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?
Logged

Offline JGK

  • Chemist
  • Full Member
  • *
  • Posts: 738
  • Mole Snacks: +66/-19
  • Gender: Male
Re: Why is the atomic weight of oxygen less than 16 when its isotopes are 16,17,18?
« Reply #1 on: December 18, 2009, 12:09:19 PM »
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.
Logged
Experience is something you don't get until just after you need it.

Offline Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 27857
  • Mole Snacks: +1813/-412
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Re: Why is the atomic weight of oxygen less than 16 when its isotopes are 16,17,18?
« Reply #2 on: December 18, 2009, 12:13:32 PM »
What is EXACT mass of 16O?

Hint: it is not 16.
Logged
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info

Offline AWK

  • Retired Staff
  • Sr. Member
  • *
  • Posts: 7976
  • Mole Snacks: +555/-93
  • Gender: Male
Re: Why is the atomic weight of oxygen less than 16 when its isotopes are 16,17,18?
« Reply #3 on: December 18, 2009, 01:44:19 PM »
Logged
AWK
Pages: [1]   Go Up
« previous next »
Sponsored Links