__________ is also known as laughing gas.

CONCEPT:

Nitrous Oxide and Its Properties

• Nitrous oxide (N₂O) is a colorless, non-flammable gas with a slightly sweet odor and taste.
• It is commonly referred to as "laughing gas" because of its euphoric effects when inhaled, which can cause laughter.
• Nitrous oxide is widely used in medicine as an anesthetic and analgesic, as well as in food preparation (e.g., as a propellant for whipped cream).
• Chemically, nitrous oxide is composed of two nitrogen atoms and one oxygen atom.

EXPLANATION:

The statement asks which compound is also known as "laughing gas".

• Nitrogen trioxide (N₂O₃) is not laughing gas; it is a chemical compound that exists in equilibrium with its dimer.
• Nitrogen pentoxide (N₂O₅) is an anhydride of nitric acid and is not laughing gas.
• Nitrous oxide (N₂O) is the correct answer, as it is commonly known as "laughing gas".
• Nitric oxide (NO) is a signaling molecule in humans and is not laughing gas.

Therefore, the correct answer is Option 3: Nitrous oxide (N₂O).