Question

which of the following isotopes should be expected to be radioactive? (a)
\ce{^{48}_{22}ti}
(b)
\ce{^{88}_{38}sr}
(c)
\ce{^{192}_{76}os}
(d)
\ce{^{244}_{94}pu}
select one: a. a b. b c. c d. d

Explanation:

1. For isotopes, elements with atomic number >83 are all radioactive, as their nuclei are too large to be stable. Additionally, check stable isotopes:

• $_{22}^{48}\text{Ti}$: Titanium-48 is a stable isotope of titanium.
• $_{38}^{88}\text{Sr}$: Strontium-88 is the most abundant stable isotope of strontium.
• $_{76}^{192}\text{Os}$: Osmium-192 is a stable isotope of osmium.
• $_{94}^{244}\text{Pu}$: Plutonium has an atomic number of 94 (greater than 83), and all isotopes of plutonium are radioactive.

Answer:

d. D ($_{94}^{244}\text{Pu}$)