Question

Uranium has three isotopes with the following percent abundances: 92234U (0.0058%), 92235U (0.71%), and 92238U(99.23%). What do you expect the atomic mass of uranium to be in whole numbers? Why?

Answer 1

The expected atomic mass of uranium in whole numbers is likely to be close to 238 due to the dominant abundance of the U-238 isotope and its contribution to the weighted average atomic mass.

Step-by-step explanation:

The student has asked about the expected atomic mass of uranium in whole numbers given the percent abundances of its three isotopes: U-234 with 0.0058%, U-235 with 0.71%, and U-238 with 99.23%.

To calculate the atomic mass of uranium, we must consider the weighted average based on these percentages and the mass numbers of each isotope.

The calculation would be as follows:

• (0.0058% × 234) + (0.71% × 235) + (99.23% × 238)

However, since we will round to whole numbers and the percentages of U-234 and U-235 are much smaller compared to U-238, we can anticipate that the whole number atomic mass is highly influenced by the mass number of U-238, which is 238. This implies that the atomic mass in whole numbers will likely be very close to 238.

The reason we can be confident with this approximation is that the small percentages of U-234 and U-235 have a minimal effect on the total calculation, leaving U-238 as the primary contributor to the overall atomic mass.