Some substances are made of separate atoms rather than molecules. Which of the following substances exists as single, unbonded atoms at room temperature?
Question 1 Report
Some substances are made of separate atoms rather than molecules. Which of the following substances exists as single, unbonded atoms at room temperature?
Answer Details
Most non-metals do not exist as lone atoms because their outer shells are incomplete, so they share electrons to form molecules. Oxygen exists as \(\mathrm{O_2}\), nitrogen as \(\mathrm{N_2}\) and chlorine as \(\mathrm{Cl_2}\), each pair of atoms joined by covalent bonds.
Argon is a noble gas in Group VIII. Its outer shell already holds 8 electrons, so it has no need to share any. With nothing to gain from bonding, argon exists as single unbonded atoms, described as monatomic. That is why argon is the substance made of separate atoms at room temperature.
The misconception behind choosing oxygen or nitrogen is treating the element symbol as the formula. The symbol \(\mathrm{O}\) names the element, but the substance in the air is \(\mathrm{O_2}\). Only the noble gases are monatomic, and that is a direct consequence of the full outer shell.
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