Which of the following substances most likely has the greatest electrical conductivity at room temperature?

• A. H_2O (pure water)
• B. C_6H_{12}O_6 (glucose)
• C. CO_2 (carbon dioxide)
• D. Na (sodium metal)

Answer: (D)

Verified step by step guidance

1. Understand that electrical conductivity depends on the presence of charged particles (ions or free electrons) that can move freely to carry electric current.
2. Analyze each substance: pure water (H_2O) is a poor conductor because it has very few ions; glucose (C_6H_{12}O_6) is a molecular compound and does not ionize in water, so it does not conduct electricity; carbon dioxide (CO_2) is a nonpolar molecular gas and does not conduct electricity.
3. Recognize that sodium metal (Na) is a metallic solid, which means it has a lattice of positive ions surrounded by a 'sea' of delocalized free electrons that can move freely, allowing it to conduct electricity very well.
4. Conclude that among the given substances, sodium metal (Na) has the greatest electrical conductivity at room temperature due to its metallic bonding and free electrons.
5. Summarize that electrical conductivity is highest in metals because of free electrons, while molecular substances and pure water have very low conductivity due to lack of free charge carriers.