Question

A photon has a mass ?

Answer 1

The atom is the smallest unit that a matter is made up of and it retains all the chemical properties of the element. This atom consists of two regions, one called the atomic nucleus and the other , the larger region consists of a cloud of electrons, which surround the atomic nucleus.

Complete answer:
The atomic nucleus is the mass of the atom and it consists of two elements – the proton and the neutron. The neutrons being neutral in charge does not contribute towards the charge while the protons have a unit positive charge of $+ 1e$ or $1.6\times {\text{ 1}}{{\text{0}}^{ - 19}}C$. The mass of the proton is $1.67262\times {10^ - }27Kg$ or 9.1{\text{ }}\times {\text{ 1}}{{\text{0}}^{ - 31}}{\text{ }}kg$$$1836$ times the mass of an electron. Other units of mass of proton are 938.27208816{\text{ MeV/}}{{\text{c}}^2}$or$1.007276466621{\text{ }}Da$$ .

Additional Information: The mass of neutron is $1839$ times of an electron or $1.674\times {10^{ - 27}}{\text{ kg}}$ and it is just slightly greater than the mass of protons. The neutron and proton form the nucleus and thus the nucleus consists of the mass of the atom and has a high density as the size of the nucleus is very small, of the range ${10^{ - 15}}m$ . The radius is very small compared to the size of the atom, which is about ${10^{ - 10}}m$ . The electrons form a cloud around the nucleus and have almost negligible mass. They have a charge of $- 1e$ and a mass of $9.1{\text{ }}\times {\text{ 1}}{{\text{0}}^{ - 31}}{\text{ }}kg$.

Note: The values of the mass and charge of electrons, protons and neutrons are commonly asked and should be remembered. The radius of the nucleus compared to an atom should also be remembered. It was discovered by Sir Ernest Rutherford in the year $1919$ and was named in $1920$.