Question

What is the difference between melting and liquefication of elements? As noble elements posses weak van der Waal's forces of attraction between them so it is easy to break bond so according to collision theory , for product formation breaking of bond is necessary , as it is easy to brake bonds of noble elements still they don't form any compound. There are only few compounds are present. Why is it so?

Answer 1

In the case of noble gases, they are inert and not reactive. This is because they have completely filled electronic configuration. For example the electronic configuration of neon is 1s2 2s2 2p6 which is completely filled 2nd shell. For element with completely filled electronic configuration removing or adding electrons will be difficult.
In other words the ionization energy of noble gases are very high due to stable electronic configuration.
But ionization energy decreases in a group due to increase in atomic size. For example xenon is having very high atomic size and the electrons are not closely bonded with nucleus. So they can be easily removed by high electronegative elements like flourine and oxygen.
So among all the rare gases xenon will easily form compounds because the atomic size is big and ionization energy is very less. Further xenon will form compounds with high electronegative elements like oxygen and flourine.
Other rare gases will not react to give compound.
Note:
Reactivity of the element is related with the bond dissociation energy only if it is forming molecule. For example nitrogen is less reactive because the energy required to break the triple bond is high.
But if there is no molecule formed then the reactivity is decided by electronic configuration only. For example both helium and sodium are in atomic state. But sodium is high reactive and helium is less reactive. Because helium is having completely filled electronic configuration while sodium is having one electron to donate.