In 1961,the reference for the atomic mass unit (amu or u)was changed from naturally occurring oxygen with a value of 16.000 u to one based on a single isotope of carbon (carbon-12).Why was it changed?
A)The atomic composition of oxygen varies depending upon its source.
B)Carbon-12 is more common than oxygen.
C)Carbon exists as only one isotope, carbon-12.
D)Carbon can combine with four atoms of hydrogen to form CH₄, methane, while oxygen only combines with two atoms of hydrogen to form water, H₂O.

Question

Quizplus · Accepted Answer

The atomic composition of oxygen varies depending upon its source, leading to variations in its atomic mass. Using carbon-12, which is a single isotope, provides a more consistent standard.

In 1961,the Reference for the Atomic Mass Unit (Amu or U)was