If the natural abundance of Br-79 is 50.69%, which of the following statements is correct regarding the isotopic composition of naturally occurring bromine?

• A. Bromine contains only one stable isotope.
• B. Br-79 and Br-81 are present in nearly equal amounts.
• C. Br-81 is much more abundant than Br-79.
• D. Br-79 is the only isotope found in nature.

Answer: (B)

Verified step by step guidance

1. Understand that natural abundance refers to the percentage of each isotope of an element found naturally on Earth.
2. Note that the problem states the natural abundance of Br-79 is 50.69%, which means that about half of naturally occurring bromine atoms are Br-79.
3. Since the total abundance of all isotopes must add up to 100%, the remaining percentage (100% - 50.69%) corresponds to the abundance of Br-81.
4. Calculate the abundance of Br-81 by subtracting the abundance of Br-79 from 100%, which will show that Br-81 is present in nearly equal amount to Br-79.
5. Conclude that bromine naturally occurs as a mixture of two stable isotopes, Br-79 and Br-81, in nearly equal proportions.