nucleus, in physics: Scientific Notation for the Nucleus and Nuclear Reactions

A nucleus may be represented conveniently by the chemical symbol for the element together with a subscript and superscript for the atomic number and mass number. (The subscript is often omitted, since the element symbol fixes the atomic number.) The nucleus of ordinary hydrogen, i.e., the proton, is represented by ₁H¹, an alpha particle (a helium nucleus) is ₂He⁴, the most common isotope of chlorine is ₁₇Cl³⁵, and the uranium isotope used in the atomic bomb is ₉₂U²³⁵.

Nuclear reactions involving changes in atomic number or mass number can be expressed easily using this notation. For example, when Ernest Rutherford produced the first artificial nuclear reaction (1919), it involved bombarding a nitrogen nucleus with alpha particles and resulted in an isotope of oxygen with the release of a proton: ₂He⁴+₇N¹⁴→₈O¹⁷+₁H¹. Note that the total of the atomic numbers on the left is equal to the total on the right (i.e., 2+7=8+1), and similarly for the mass numbers (4+14=17+1).

Sections in this article:

• Introduction
• Scientific Investigations of the Nucleus
• Scientific Notation for the Nucleus and Nuclear Reactions
• Models of the Nucleus
• Mass Defect, Binding Energy, and Nuclear Reactions
• Size and Density
• Composition
• Bibliography

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