Which of the following is a radioactive isotope used in the treatment of cancer? MCQ with Answer and Explanation

Explanation:
Nitrogen has 5 valence electrons; it needs 3 more to complete the octet. It shares three electrons with three hydrogen atoms, forming three covalent bonds. Therefore, valency is 3. In the case of nitrogen, covalency is 3, while its electrovalency could be 5 (losing all 5). For covalent molecules, valency = number of shared electron pairs. In N₂, valency is also 3 (triple bond).

Explanation:
Chlorofluorocarbons (CFCs), once widely used as refrigerants and propellants, are the primary culprits behind ozone depletion. When CFCs reach the stratosphere, UV radiation breaks them down, releasing chlorine atoms. A single chlorine atom can catalytically destroy thousands of ozone (O3) molecules.

Explanation:
Copper pyrites, also known as chalcopyrite, is the most important and abundant ore of copper. Its chemical formula is CuFeS2. Bauxite is the ore of aluminum, cinnabar is the ore of mercury, and haematite is the primary ore of iron.