isotope

History

The term 'isotope' was proposed by Frederick Soddy in 1913. He noticed that radioactive elements could occupy the same place in the periodic table but have different atomic masses.

How it works

The properties of isotopes are determined by the number of neutrons. In nature, most elements are a mixture of stable isotopes, but there are also radioactive ones. Analogy: like in a family, children may be of the same height but different weights—they have similar character (chemical properties) but different physical parameters.

History

The term 'isotope' was proposed by Frederick Soddy in 1913. He noticed that radioactive elements could occupy the same place in the periodic table but have different atomic masses.

How it works

The properties of isotopes are determined by the number of neutrons. In nature, most elements are a mixture of stable isotopes, but there are also radioactive ones. Analogy: like in a family, children may be of the same height but different weights—they have similar character (chemical properties) but different physical parameters.

History

After the discovery of radioactivity by Becquerel in 1896, Ernest Rutherford and Frederick Soddy showed in 1902 that radioactive decay is accompanied by the transmutation of elements. In 1913, Soddy introduced the term 'isotope' for chemically indistinguishable radioelements with different masses. That same year, J.J. Thomson discovered neon isotopes of masses 20 and 22. The discovery of the neutron by James Chadwick in 1932 explained the existence of isotopes. Today, the study of isotopes underlies a multitude of methods: from radiocarbon dating to nuclear medicine.

How it works

The difference in neutron number leads to a difference in nuclear binding energy, which determines stability. According to the liquid drop model and the Weizsäcker formula, the binding energy depends on Z and A. Radioactive isotopes decay according to the radioactive decay law N(t)=N₀e^{-λt}. Mass spectroscopy allows separating isotopes by mass-to-charge ratio. Quantum effects such as tunneling explain α-decay. The Pauli principle governs the filling of nuclear shells, and neutron resonances play a role in neutron capture.

Open problems & fun facts

Prediction of stability limits of superheavy isotopes (island of stability); Measurement of isotope lifetimes with high precision for astrophysics; Understanding nucleosynthesis mechanisms in extreme astrophysical conditions; Creation of isotopes with exotic proton-to-neutron ratios

💡 Deuterium and tritium—isotopes of hydrogen—are used for thermonuclear fusion. If we mastered controlled fusion, ocean water would become an inexhaustible energy source, as it contains plenty of deuterium.