Question

Rubidium-79 decays by positron emission and forms Krypton-79, which is a gas. A weighed 100.00 mg sample of solid rubidium-79 was allowed to decay for 42 minutes, then weighed again. Its mass was 25.00 mg. What is the decay product of Rubidium-79 when it undergoes positron emission?

A) Krypton-79
B) Xenon-79
C) Argon-79
D) Radon-79

Answer 1

the decay product of Rubidium-79 when it undergoes positron emission is Xenon-79. Thus, the corret option is B.

Step-by-step explanation:

Rubidium-79 undergoes positron emission, transforming into a new element. To determine the decay product, we compare the initial and final masses. The decrease in mass indicates the conversion of rubidium-79 into a lighter element. The correct answer is B) Xenon-79. Positron emission involves the conversion of a proton into a neutron, resulting in the emission of a positron (a positively charged electron). The newly formed element, in this case, is Xenon-79.

To explain further, when rubidium-79 undergoes positron emission, a proton within the nucleus is converted into a neutron, leading to the formation of a new element with one less proton.

Xenon-79 has one less proton compared to rubidium-79. The emitted positron is not included in the final product because it is expelled from the nucleus. The mass change observed during the decay process aligns with the conversion from rubidium-79 to xenon-79. Understanding the principles of nuclear decay and the resultant changes in atomic composition is fundamental in predicting the decay products of radioactive elements.