1) boiling points increase as molecular weight increase and vice versa. This is due to the increase in van der waals forces between molecules. 2) branching decreases the melting and boiling i.e increase in branching decrease boiling point and melting point. This is due to the fact that there are less point of contact between neighbouring molecules, so molecules are farther apart from each other, which means weaker van der waals(London forces) less energy is required to overcome these force of attraction. 3) In homolytic fission each of the fragment retain one of the bonded electron and radicals are made if the molecule is neutral. In heterolytic fission one fragment gets both bonding electron. The energy for the heterolytic fission is higher because energy is not only needed to break the covalent bond but also to overcome the force of attraction between oppositely charged ions formed.
The stability of atoms depends on whether or not their outer-most shell is filled with electrons. If the outer shell is filled, the atom is stable. Atoms with unfilled outer shells are unstable, and will usually form chemical bonds with other atoms to achieve stability.
