How many elements exists in gaseous state under Normal conditions?

Question

Accepted Answer

The correct option is (2):

Under normal conditions (Standard Temperature and Pressure, STP, which is $0^\circ \mathrm{C}$ or $273.15 \mathrm{K}$ and $1 \mathrm{atm}$ pressure), there are 11 elements that exist in a gaseous state. These elements can be broadly classified into two categories: noble gases and certain non-metals. The noble gases, located in Group 18 of the periodic table, are helium ($\mathrm{He}$), neon ($\mathrm{Ne}$), argon ($\mathrm{Ar}$), krypton ($\mathrm{Kr}$), xenon ($\mathrm{Xe}$), and radon ($\mathrm{Rn}$). These elements are monatomic and are known for their extreme stability and unreactivity due to their full valence electron shells. In addition to the noble gases, there are five diatomic non-metals that are gases at normal conditions: hydrogen ($\mathrm{H_2}$), nitrogen ($\mathrm{N_2}$), oxygen ($\mathrm{O_2}$), fluorine ($\mathrm{F_2}$), and chlorine ($\mathrm{Cl_2}$). These elements form stable diatomic molecules, and their intermolecular forces are weak enough that they remain in a gaseous state at room temperature and standard pressure. Therefore, summing these up, we have $6$ noble gases $+ 5$ diatomic non-metals $= 11$ elements in total.

The incorrect option is (1): The number 10 is incorrect as it omits one of the 11 gaseous elements at normal conditions.
The incorrect option is (3): The number 12 is incorrect as it overcounts the actual number of gaseous elements.
The incorrect option is (4): The number 14 is incorrect as it significantly overestimates the number of elements that are gases under normal conditions.