Which statement about noble gases is true?

Which statement about noble gases is true?

• A. Highly reactive with water
• B. Have low ionization energies
• C. Monoatomic, colorless gas
• D. Form diatomic molecules

Answer: (C)

Noble gases have filled outer electron shells, which makes them extremely stable and largely unwilling to form bonds. Because of this, they exist as isolated atoms rather than bonded units, so they are monoatomic gases that are colorless at room temperature. This is why the statement describing them as monoatomic, colorless gases is the true one. Their complete valence shells also explain their high ionization energies—they resist removing an electron. They do not react with water and they do not form diatomic molecules under normal conditions, so those statements are not correct.

Noble gases have filled outer electron shells, which makes them extremely stable and largely unwilling to form bonds. Because of this, they exist as isolated atoms rather than bonded units, so they are monoatomic gases that are colorless at room temperature. This is why the statement describing them as monoatomic, colorless gases is the true one. Their complete valence shells also explain their high ionization energies—they resist removing an electron. They do not react with water and they do not form diatomic molecules under normal conditions, so those statements are not correct.