Physics · nuclei · NEET
It is a nuclear process, not a chemical one. Radioactivity happens inside the nucleus of the atom, not in the outer electrons. That is why heating, cooling, or mixing chemicals does NOT change how fast a substance decays. Chemical reactions only involve electrons; radioactivity involves the protons and neutrons in the core.
A nucleus is stable only when its neutron-to-proton ratio is right. For light nuclei this ratio is about 1:1, and for heavy nuclei it rises to about 3:2 because more neutrons are needed to fight the repulsion between protons. If a nucleus has too many or too few neutrons, it is unstable and decays to reach a stable ratio.
Alpha decay emits an alpha particle, which is a helium nucleus (2 protons + 2 neutrons, written as He-4). Beta decay emits a beta particle, which is an electron (beta-minus) or a positron (beta-plus). Gamma decay emits a gamma ray, which is a high-energy photon (electromagnetic radiation), not a particle of matter.
No. In gamma decay the nucleus only releases extra energy by jumping from a higher energy level to a lower one. No protons or neutrons leave, so both the atomic number Z and mass number A stay the same. Only alpha and beta decay change the identity of the nucleus.
No. Radioactive decay is a spontaneous and random event for each nucleus. You cannot force a nucleus to decay or stop it with temperature, pressure, or chemistry. We can only predict decay for a large group using half-life; we can never say exactly when one single nucleus will decay.
Decay is the event: an unstable nucleus transforming into a different, more stable nucleus. Radiation is the alpha, beta, or gamma that comes out during that event. So decay is the process, and radiation is the product that is emitted.
A. H. Becquerel discovered radioactivity in 1896, purely by accident, while studying uranium salts. He found they gave out rays that could pass through paper and darken a photographic plate.
Alpha decay (emits a helium nucleus, He-4), beta decay (emits an electron or a positron), and gamma decay (emits a high-energy photon). These are the standard three decays in the NEET Nuclei chapter.
Gamma rays are the most penetrating because they are high-energy photons with no charge or mass. Alpha particles are the least penetrating and are stopped even by paper or skin. Beta lies in between.
It is a sign of an unstable nucleus. A nucleus that is away from the stable neutron-to-proton ratio (too many neutrons or protons) decays to move toward stability.
No. The decay rate depends only on the nucleus itself (its decay constant). Temperature, pressure, and chemical state do not change it, because decay happens deep inside the nucleus.
