Question

If atoms are not able to exist independently, what about argon (Ar), helium (He) ; it made of 1 atom only right? So therefore how thats able to exist?
And hydrogen (H2) , is made of 2 atoms right? So why hydrogen is not able to exist independently?

Answer 1

Most atoms of elements do not have octet and they try to attain noble gas configuration , that's why they react and form bonds and cannot exist independently.

Helium (²He), Neon (¹⁰Ne), Argon (¹⁸Ar), and Krypton (³⁶Kr). These special atoms are the most common of the noble gases. They are called "noble" because they don't usually bond with other atoms to make molecules, and because they are all gases at room temperature we call them "the noble gases".
Hydrogen has half-filled valence shell (with a 1s1 configuration) with one e− also causes hydrogen to act like a halogen non-metal to gain noble gas configuration by adding an additional electron
H2 has very strong intramolecular forces; H2 reactions are generally slow at room temperature due to strong H—H bond. H2 is easily activated by heat, irradiation, or catalysis. Activated hydrogen gas reacts very quickly and exothermically with many substances.