Molecular terminology – what does “triatomic” mean? In kinetic theory and chemistry, a triatomic molecule contains how many atoms in a single molecule?

Introduction / Context:
Molecular descriptors such as monatomic, diatomic, and triatomic indicate the number of atoms bonded together to form a single molecule. These distinctions influence molecular degrees of freedom and thus thermodynamic properties like specific heats and heat capacities.

Given Data / Assumptions:

• Standard definitions in chemistry and physics.
• Examples include O3 (ozone) and CO2 as triatomic molecules.
• Ideal-gas approximations often classify molecules by atom count and geometry.

Concept / Approach:

“Triatomic” literally means “containing three atoms.” In kinetic theory, triatomic molecules may be linear (CO2) or non-linear (H2O), affecting rotational and vibrational degrees of freedom and thereby specific heat values at various temperatures.

Step-by-Step Solution:

Verification / Alternative check:

Periodic and molecular nomenclature consistently use these prefixes; spectroscopy and thermodynamic data for triatomic species reflect the additional modes compared with monatomic and diatomic gases.

Why Other Options Are Wrong:

One or two atoms describe mono- and diatomic species; four or five do not match “tri-”.

Common Pitfalls:

Assuming all triatomic molecules are linear; geometry varies and influences properties.

Final Answer:

three