Physics · Composition and size of nucleus, atomic masses, mass-energy relation, mass defect

Naturally occurring argon (Ar) consists of three isotopes the atoms of which occ

Naturally occurring argon (Ar) consists of three isotopes the atoms of which occur in the abundances as given in the table The atomic weight of argon is: Isotopes Abundance \( ^{36} A r \) 0.34\% \( ^{38} A r \) 0.07\% \( \begin{array}{ll}40 & \text { 99.59\% }\end{array} \)

  • A. 38.45 u
  • B. 37.20
  • C. 39.98 и
  • D. 40.98 u

Step-by-step solution

The atomic weight is the weighted average of isotopic masses. Using approximate masses 36, 38, 40 u and abundances 0.34%, 0.07%, 99.59% gives (36×0.34 + 38×0.07 + 40×99.59)/100 = 39.98 u.
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