The electrons have moved from lower energy level to higher energy level.
4. Pure hydrogen peroxide (H2O2) is a bit thick in consistency and its boiling point is 1520C. The atoms in hydrogen peroxide are in the order HOOH in terms of intermolecular forces, why does hydrogen peroxide have different physical properties than water
For Hcl, the chlorine gas alone has a boiling point of -350C. Therefore chlorine has a higher boiling point than fluorine, which is of the same group because of increase in size of molecule in chlorine.
When chlorine reacts with hydrogen to from Hcl, a covalent bond is created. This bond is stronger than the forces of attraction between molecules and therefore require more energy to break hence higher boiling point.
It should be noted that these are gases and gases have low boiling point. Hcl can form Hcl acid, which is a liquid with high boiling point. Therefore Hcl is has the highest boiling point followed by Argon and F2 has the lowest.
They all have eight electrons in their outermost energy level (full) hence have negligible tendency to gain or lose electrons. Therefore stable and non-reactive. Atomic radius increases down the group due to increase in number of energy levels. And weak forces of attraction between atoms.
As the atomic size increase down the group there is increase in strength of attrac ...