Dear beloved readers, welcome to our website! We hope your visit here brings you valuable insights and meaningful inspiration. Thank you for taking the time to stop by and explore the content we've prepared for you.
------------------------------------------------ Select the best evidence to support the statement that U-235 is rare.

1. U-235 is found in very small quantities in natural uranium.
2. U-235 is the most abundant isotope of uranium.
3. U-235 is easily obtained from common sources.
4. U-235 is highly stable and does not decay.

U-235 is rare because it comprises less than 1% of natural uranium, necessitating a complex and costly enrichment process to increase its concentration for use in nuclear reactors or weapons.

Explanation:

The best evidence to support the statement that U-235 is rare is that U-235 is found in very small quantities in natural uranium. This is correct because naturally occurring uranium is composed of more than 99% uranium-238 and less than 1% uranium-235, which is the fissionable isotope necessary for an atomic bomb.

To use uranium as a fuel for nuclear reactors, its U-235 content must be increased through a process known as enrichment. For nuclear weapons, this enrichment process must result in uranium being enriched to 70% or more of U-235; otherwise, the chain reaction required for an explosion cannot be sustained. The significant effort and resources required to enrich uranium-235 underscore its scarcity.