Question

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5. (a) We have a collection of Hydrogen atoms in the ground state. They are bombarded with hotons of energy 12.1 MeV. What are the energies of the photons that can be emitted by the excited Hydrogen atoms? Answer either b or c b. Why do the more stable high A elements generally have more neutrons than protons? (c) Why do fission and fusion relcase much more energy than chemical burning or a chemical explosion? 53 g10 3 sec 6011 37 e1.6x10"C 4 G-20% x10-11- F = ma v-oat 2 Fmg Fs = kx V = IR P=VI =12 R E-0 ev n-4 E-:-.85 ev n-3 E =-1.5eV -13.6 -3.4 ev n-2 E

Answer 1

a)the binding energy or the energy required to ionize hydrogen atom is given by equation,

, so for ground state that is n=1,energy required =13.6ev to ionize.

一13.6 En-

Since the energy required to excite an atom in ground state is largest , giving energy greater than that energy that is 13.6ev, will create a free electron or ionize the atom.(to excite to higher energy states for eg. n=2 energy required is -3.4-(-13.6)=10.2 which is smaller than binding energy of ground state)

so in the question photons of energy 12.1 Mev is given which is very large.This will ionize the atom. So no electrons will be available for de-exciting to lower energy state to emit a photon.so no photons are emitted.

b)Nuclear force is the force that binds nuetrons and protons together. It is very strong compared to electrostatic force and it is also short in range. So as the atoms become bigger or heavier more protons and nuetrons are added. These protons are repulsive in nature, but nuetrons are nuetral. So as more protons are added electrostatic force slightly holds an upper hand as the range of force is increased. so protons may decay via alpha decay or spontaneous fission. so nuetron number is slightly higher than proton number in heavier atoms.

c)Nuclear fission or fusion takes place in the scale of nucleus in which the reaction takes place against strong nuclear force , which is 137 times more powerful than electromagnetic force. so the energy stored in a nuclear bond is on the order of 1Mev where as for chemical bond it is of the order of 1ev that is approximately one million times less. Due to this reason nuclear fission or fusion releases more energy than chemical burning or explosions.