Which of the following characteristics is common to hydrogen, nitrogen, oxygen and carbon dioxide?

Hydrogen (H2), nitrogen (N2), oxygen (O2), and carbon dioxide (CO2) are all gases at room temperature and standard atmospheric pressure [1]. While hydrogen, nitrogen, and oxygen are diatomic elemental molecules [2], carbon dioxide is a triatomic molecular compound consisting of one carbon atom and two oxygen atoms [2]. Therefore, they are not all diatomic. Regarding other properties, these gases are generally colorless in their standard states, and they exhibit vastly different chemical reactivities; for instance, nitrogen is relatively inert due to its triple bond [2], while oxygen is a strong oxidant. Hydrogen is highly flammable [1], and carbon dioxide is a stable product of combustion. Thus, the only common characteristic among the four listed is their physical state as gases at room temperature.

Sources

1. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 20: Earths Atmosphere > Permanent Gases of The Atmosphere > p. 271
2. [2] Science , class X (NCERT 2025 ed.) > Chapter 4: Carbon and its Compounds > 4.1 BONDING IN CARBON – THE COVALENT BOND > p. 60