In this physics iit jee video lecture, we will be discussing nuclear physics. The topics covered in this JEE video are,

• Nucleus
• Nucleons

So what is a nucleus? In atomic structure, we have seen that the atom is made up of nucleus and electrons. The electrons move in orbital motion. Nucleus has all the mass concentrated in it. The protons are denoted by p and the neutrons are denoted by n. The size of the nucleus is nearly 100 times smaller than the size of an atom. The nucleus consists of neutron and proton.

X = nucleus of element X

A Xz   , here z is the number of protons= atomic number;

A is the atomic mass number = sum of number of protons and number of neutrons in a nucleus.

A number of neutrons are (A-Z). Neutron is a charge less particle. It was discovered by Chadwick and is unstable outside the nucleus. Further, in the video, we have discussed Nucleons. Nucleons mean that particle which lie in the nucleus. Neutrons and protons are called nucleons, as they lie inside the nucleus. Electrons do not lie inside the nucleus. The wavelength associated with the electron is greater than the size of the nucleus, thus nucleus cannot accommodate electrons. N is the number of neutrons.

Mass of neutron, Mn = 1.674 X 10 -27Kg = 1.008 u

Mass of proton is, Mp = 1.673 X10 -27Kg = 1.007 u

Mass of electron is,  Me = Mp/1837

1 Atomic Mass unit or 1 a.m.u. is

1 u =  (Mass of C12 atom) = 1.660539 X 10 -27 Kg

The next jee physics video topic discussed is nuclear radius. By an experiment we found out that nucleus is closely packed.

R = R0 A1/3      ;   R0 = 1.2 fm = 1.2 10-15 m ; 1 fm = 10-15 m

The volume of nucleus is directly proportional to its atomic mass umber.

Volume ;    R3  proportional to A;             R = kA1/3

The nuclear density is constant for every atomic nucleus.

Further we have discussed about isotopes, isobars, isotones and isomers.