Q. Radioactive decay of which of the following isotopes in the Earth’s crust leads to generation of argon?
Answer: K-40
Notes: The radioactive decay of potassium-40 (K-40) isotopes in the Earth's crust leads to the generation of argon. Potassium-40 is a naturally occurring radioactive isotope of potassium, and it undergoes a process called beta decay. During this decay, a potassium-40 nucleus transforms into a stable argon-40 (Ar-40) nucleus by emitting a beta particle (an electron) and an antineutrino. This process is known as the "potassium-argon" (K-Ar) decay, and it is commonly used in geochronology to determine the ages of rocks and minerals. As potassium is abundant in the Earth's crust, the decay of potassium-40 and the subsequent production of argon-40 occur naturally and play a crucial role in dating geological materials.