What common object contains hydrogen and is associated with the property of containing the lightest atom in the universe?

What common object contains hydrogen and is associated with the property of containing the lightest atom in the universe?

• A. Water; lightest atom in the universe
• B. Charcoal; lightest atom in the universe
• C. Salt; lightest atom in the universe
• D. Air; lightest atom in the universe

Answer: (A)

Hydrogen is the lightest element, so its atom is the lightest. Water is a common compound that clearly contains hydrogen in its formula, H2O, with two hydrogen atoms per molecule. That direct link makes water the best match for the idea of containing the lightest atom in the universe. Charcoal is mainly carbon, salt is sodium chloride with no hydrogen in the main formula, and air is mostly nitrogen and oxygen with only trace hydrogen—so they don’t embody the association as clearly as water does.

Hydrogen is the lightest element, so its atom is the lightest. Water is a common compound that clearly contains hydrogen in its formula, H2O, with two hydrogen atoms per molecule. That direct link makes water the best match for the idea of containing the lightest atom in the universe. Charcoal is mainly carbon, salt is sodium chloride with no hydrogen in the main formula, and air is mostly nitrogen and oxygen with only trace hydrogen—so they don’t embody the association as clearly as water does.