Question
$${m_p}$$ and $${m_n}$$ are masses of proton and neutron respectively. An element of mass $$m$$ has $$Z$$ protons and $$N$$ neutrons, then
A.
$$m > Z{m_p} + N{m_n}$$
B.
$$m = Z{m_p} + N{m_n}$$
C.
$$m < Z{m_p} + N{m_n}$$
D.
$$m$$ may be greater than, less than or equal to $$Z{m_p} + N{m_n},$$ depending on nature of element
Answer :
$$m < Z{m_p} + N{m_n}$$
Solution :
When a nucleus is formed, then the mass of nucleus is slightly less than the sum of masses of $$Z$$ protons and $$N$$ neutrons.
i.e, $$m < \left( {Z{m_p} + N{m_n}} \right)$$