Nucleus
Nucleus is the dense inner part of an Atom which contains 99.9% mass of an Atom. Atomic radius is of the order of 10−8 cm and the nuclear radius is of the order of 10−13 cm.
Composition of Nucleus
It contains Neutrons and Protons
Atomic Mass Unit
A unit used to measure very small mass such as of an Atom. It is defined as 1/12 of mass of a single Atom of C-12 (an isotope of Carbon). It is represented as u (unified Atomic mass unit) or amu (Atomic mass unit).
1 amu = 1/12 of mass of one C-12 atom (1.99 x 10-26 Kg) = 1.66 x 10-27 Kg
Mass Spectrometer
Isotopes
Isotopes are types of atoms of an Elements having same number of Protons but different numbers of Neutrons. In other words, they have same Atomic Number but different Mass number. Example: 1H1 (Protium) , 1H2(Deuterium), 1H3 (Tritium) are isotopes of Hydrogen in which Tritium is Radioactive.
Atomic mass
Atomic weight
The Periodic table generally shows Atomic weight (Relative Atomic mass) of an element. It is a weighted average of masses all known Isotopes of an element.
Subatomic Particles
| Particle Name | Symbol | Mass in Kg | Mass in u** or amu***) | charge in C* | Discovered By (Year) – Experiment |
| electron | e– | 9.1 × 10−31 | 0.0005486 | – 1.6 x 10-19 | J. J. Thomson (1897) – cathode ray experiment |
| proton | p+ | 1.67 × 10−27 | 1.007276 | – 1.6 x 10-19 | 1. Observed as H+ by E Goldstein (1886) – Discharge Tube 2. Identified and named by Ernest Rutherford (1920) – Alpha (α) Particle experiment |
| neutron | n0 | 1.67 × 10−27 | 1.007276 | No charge | James Chadwick (1932) – Alpha (α) Particle Bombardment on Beryllium |
Top GK Insights
- Ernest Rutherford is known as the father of nuclear physics. he also coined the terms alpha rays and beta rays.
- Eugen Goldstein is the discoverer of anode rays or canal rays.
- James Chadwick led the British team in the Manhattan Project which produced the first nuclear weapons during World War II.