Question

Size of nucleus is measured in:
A. amu
B. angstrom
C. fermi
D. cm

Answer 1

Hint: Nucleus is the core part of an atom. It consists of protons and neutrons. The size is very small so the measurement is expressed by using the smallest unit.

Complete step by step answer: From the study of atomic models we have learnt about certain things regarding the structure of atoms. An atom mainly consists of a nucleus and empty spaces inside. The nucleus is the core of the atom which is positively charged due to presence of a proton and accounts for the mass of the atom due to presence of neutrons.
As neutrons have no charge so the nucleus is positively charged. Besides protons and neutrons, electrons are present surrounding them which carry unit negative charge. As a result the whole charge on the atom gets neutralized. All subatomic particles are present in every molecule or substance.
The size of atoms is roughly the same. For our convenience angstrom $(A^o)$ is used as the measurement unit of length to determine the atomic sizes expressed as $${10}^{-10}$$ metre. In general the radius of an atom is between $[1-2]A^o$. The size of the nucleus is smaller compared with the overall size of the atom. So a definite unit of length measurement is required to express the size.
The nucleus takes up only $${10}^{-14}$$metres of the space of the atom. As a result a convenient unit of length is employed for measuring nuclear sizes called as the femtometre ($$fm$$), which equals $${10}^{-15}$$metre. Thus the correct answer is option C, i.e. size of nucleus is measured in fermi also called femtometre.

Note: The diameter of a nucleus varies in the range of $$4-15fm$$ for a lighter nucleus to a heavy nucleus. All the mass of the atom is concentrated in the nucleus regardless of the small size. The neutrons are responsible for the masses or weight of the nucleus and the atom.