How many elements exist as gases at room temperature (approximately 25°C and 1 atm)?

• A. 2
• B. 7
• C. 18
• D. 11

Answer: (D)

Verified step by step guidance

1. Identify the elements that are gases at room temperature (approximately 25°C and 1 atm). These include the noble gases, some nonmetals, and a few diatomic molecules.
2. List the noble gases: helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). All of these are gases at room temperature.
3. List the diatomic gases: hydrogen (H₂), nitrogen (N₂), oxygen (O₂), fluorine (F₂), and chlorine (Cl₂). These elements exist as gases under standard conditions.
4. Count the total number of gaseous elements by adding the noble gases (6) and the diatomic gases (5), which gives the total number of gaseous elements at room temperature.
5. Confirm that no other elements are gases at room temperature by checking the periodic table and standard physical states of elements.