Which metallic element has atomic number 92 and includes the isotope U-235 used in power plants and weapons?

Which metallic element has atomic number 92 and includes the isotope U-235 used in power plants and weapons?

• A. Plutonium
• B. Thorium
• C. Radium
• D. Uranium

Answer: (D)

Atomic number identifies the element, and 92 corresponds to uranium, a heavy metallic element. The isotope U-235 is special because it is fissile—when a neutron hits U-235, it splits and releases energy plus more neutrons, which can start a self-sustaining chain reaction. In power plants, this chain reaction is carefully controlled to turn heat into electricity. In weapons, the reaction is rapid and unchecked, producing a massive energy release. Natural uranium contains only a small amount of U-235, so fuel is enriched to increase that fraction for reactors. The key idea is that uranium is the metal with atomic number 92, and U-235 is the isotope used for fission in both civilian and military contexts.

Atomic number identifies the element, and 92 corresponds to uranium, a heavy metallic element. The isotope U-235 is special because it is fissile—when a neutron hits U-235, it splits and releases energy plus more neutrons, which can start a self-sustaining chain reaction. In power plants, this chain reaction is carefully controlled to turn heat into electricity. In weapons, the reaction is rapid and unchecked, producing a massive energy release. Natural uranium contains only a small amount of U-235, so fuel is enriched to increase that fraction for reactors. The key idea is that uranium is the metal with atomic number 92, and U-235 is the isotope used for fission in both civilian and military contexts.