Question

Nuclear sizes are expressed in a unit named:
A. Fermi
B. Angstrom
C. Newton
D. Tesla

Answer 1

Hint: Fermi or femtometer is a unit of length. It is equal to ${{10}^{-15}}m$. The size of the nucleus is expressed in this unit. Angstrom is also a unit of length. It is equal to ${{10}^{-10}}m$. The size of the atom is expressed in this unit.

Complete Step By Step Solution:
Nucleus is the central part of an atom which comprises an almost complete mass of atoms. It consists of protons and neutrons. The size of the nucleus of an atom is very small as compared to an atom. The radius of nucleus of an atom with atomic mass A is given by the formula
$R={{R}_{0}}{{A}^{\dfrac{1}{3}}}$ ,
Where ${{R}_{0}}=1.2\times {{10}^{-15}}m$
So, the size of the nucleus is of the order of ${{10}^{-15}}m$. Femtometer is a S.I. unit of length and is equal to ${{10}^{-15}}m$. So, the size of the nucleus is expressed in femtometer or fermi. Femtometer is represented by fm.

Additional Information:
Protons, neutrons and electrons are subatomic particles i.e. they are found inside an atom. Protons are positively charged, electrons are negatively charged and neutrons are electrically neutral. Protons and Neutrons are present in a small region known as nucleus. They are held together by nuclear forces which are stronger than their repulsion due to electrostatic forces. As a result, they are not free to move outside the nucleus. Electrons are much lighter than the protons and are present outside the nucleus.

Note: The size of atom is of the order of ${{10}^{-10}}m$ while that of nucleus is ${{10}^{-15}}m$. So the atom is very large compared to that of the nucleus. For example, the size of Uranium nucleus is about 11 fm while the size of an atom of Uranium is about 2,30,000 fm.