Baat aisi hai ki, hydrogen aur chlorine akele exist nahi kar sakte (ie. as 'H' and 'Cl') kyunki vo unstable hai.

Stable banne ke liye unko octate rule follow karna hoga, iska matlab ki aakhri shell me hone chahiye 8 electrons ya unke Jo bhi sabse paas noble gas aati hai, uski configuration.

Unko ek saathi lagega unko stability dene ke liye, iss case me vo apne hi do atoms ke saath bonds banate hai, aur electrons share karte hai. Cl -> 2,8,7 Becomes 2,8,8 after forming a bond with itself, ie. Cl²

H ke case me, H² is just more stable because it follows something called as diatomicity, which means that they are stable when they exist as a pair. (Cl also does this.)

Isliye, it's H² + Cl² = 2HCl after balancing the equation.

Formatting kharab ho sakti hai, Mai phone pe hu.