NTA Abhyas JEE Main2020PhysicsNuclear PhysicsPractice
A radioactive nucleus (initial mass number A and atomic number Z ) emits 3 α - p a r t i c l e s and 2 positrons. The ratio of the number of neutrons to that of protons in the final nucleus will be
Options
- AA - Z - 8 Z - 4
- BA - Z - 4 Z - 8
- CA - Z - 12 Z - 4
- DA - Z - 4 Z - 2
Correct answer
B. A - Z - 4 Z - 8
Step-by-step solution
In positive beta decay a proton is transformed into a neutron and a positron is emitted. p + → n 0 + e + Number of neutrons initially was A - Z . Number of neutrons after decay ( A - Z ) - 3 × 2 (due to alpha particles) + 2 × 1 (due to positive beta decay). The number of protons will reduce by 8 [as 3 × 2 (due to alpha particles) + 2(due to positive beta decay)]. Hence, atomic number reduces by 8. So, the ratio number of neutrons to that of protons = A - Z - 4 Z - 8