Question

cl is less stable than F why ​

Answer 1

Fluorine , with atomic number 9 and E.C. 1s2-2s2-2p5 , it is having a very small atomic radius due to increased S character and Z/e ratio.

Fluorine is having outermost Second orbital but Chlorine has outermost third orbital.

The energy of third orbital > energy of second orbital.

hence Fluorine is less energetic as compared to Chlorine.

Energy is inversely proportional to Stability.

hence , Fluorine is more stable than Chlorine.

also ,

there is a rule that states , more negative charge on more electronegative atom is always a stable atom.

Electronegativity of fuorine is greater than chlorine and fluorine is also having Negative charge making it more stable than Chlorine.