Heavy nuclie are unstable due to large repulsive forces between large number of protons in the nucleus.

The Heisenberg Uncertainty principle explains why we cannot simultaneously determine both the precise velocity and position of a particle. This principle is only applicable at the atomic level.

Werner Heisenberg

The free proton (a proton not bound to nucleons or electrons) is a stable particle that has not been observed to break down spontaneously to other particles.

Since an atom has a finite number of protons and neutrons, it will generally emit particles until it gets to a point where its half-life is so long, it is effectively stable. It undergoes something known as “alpha decay,” and it’s half-life is over a billion times longer than the current estimated age of the universe.

Because of the various conservation laws of particle physics, a proton can only decay into lighter particles than itself. It cannot decay into a neutron or any other combination of three quarks. The decay must conserve charge, teaching us that we’d still need to have a positively charged particle in the end.

This radioactive decay, known as beta decay, is possible because the mass of the neutron is slightly greater than the proton. The free proton is stable. The neutron is unstable in a nucleus when the mass of this nucleus is higher than the sum of the masses of the daughter nucleus + electron + antineutrino.

Light nuclei are most stable if N=Z, while heavy nuclei are more stable if N>Z. (N→ number of neutrons, Z→ number of protons).

Mononeutron: An isolated neutron undergoes beta decay with a mean lifetime of approximately 15 minutes (half-life of approximately 10 minutes), becoming a proton (the nucleus of hydrogen), an electron and an antineutrino. Its existence has been proven to be relevant for nuclear structure of exotic nuclei.

neutron

(ii) has the largest charge to mass ratio, (iii) when removed leaves a different isotope of the element. (b) An particle is the same as a nucleus of helium..Q13.

Electron

electron