The RF ( retention factor ) is calculated with this formula
= distance travelled / distance travelled by solvent
And the larger the RF factor of a compound the less polar the compound ( i.e. it will not stick to the stationary phase ) hence it is better the RF values of the components to be closer
6 neutrons. The mass number is the number of protons and neutrons in the nucleus of an atom. The atomic number shows how many protons. Subract the atomic number from the mass number to find the number of neutrons.