Question

The liquid drop model of nucleus was developed by
A) Bohr, Wheeler
B) Fermi
C) Rutherford
D) Chadwick

Answer 1

Hint: Liquid drop model is a proposed model of nuclear physics which is used to approximate the mass of a nucleus using its mass number and atomic number, i.e. number of proton and neutron present. This model is based partly on theory and remaining on empirical models.

Explanation:
First this liquid drop model was proposed by George Gamow. Later around 1935 it was properly formulated by Wheeler and Bohr. This model is also known as semi-empirical mass formula. In this model nucleus is treated as a drop of incompressible fluid of very high density. They are held together by the nuclear force (one type of strong force). This model provides a fairly rough estimation of binding energy of the nucleus and that gives a rough estimation of nucleus mass. According to this theory mass of a nucleus is given as:
$m = Z{m_p} + N{m_n} - \dfrac{{{E_B}(N,Z)}}{{{c^2}}}$
Where, m is the mass of nucleus, Z and N are proton and neutron number, ${m_p}$and ${m_n}$are mass of a proton and neutron, ${E_B}$is binding energy of nucleus and c is velocity of light. Now, this binding energy is a combined effect of Volume energy, surface energy, coulomb energy, asymmetry energy and pairing energy. All these energy terms depend on the proton and neutron numbers of nucleus and the coefficients of these terms are empirically determined from experimental data.

Correct answer:The liquid drop model of nucleus was developed by (a) Bohr, Wheeler.

Note: This liquid drop model provides a good fit for heavier nuclei, but gives a poor fit to very light nuclei cause this model doesn’t consider the inner shell structure of the nucleus. Also, given the atomic number this model provides neutron and proton ratio estimation which is fairly accurate.