By the end of this lesson you should be able to read, write and interpret the nuclide notation $^{A}_{Z}\text{X}$ and use it confidently in calculations involving nuclear reactions.
1. What the Symbols Represent
$\text{X}$ – chemical symbol of the element (e.g., C for carbon, U for uranium).
$Z$ – atomic number, the number of protons in the nucleus.
$A$ – mass number, the total number of nucleons (protons + neutrons) in the nucleus.
$N$ – number of neutrons, given by $N = A - Z$.
2. Reading the Notation
The standard format is $^{A}_{Z}\text{X}$, where the mass number $A$ is placed as a superscript to the left of the element symbol and the atomic number $Z$ as a subscript. Example:
$$^{14}_{6}\text{C}$$
means a carbon nucleus with $A=14$ (total nucleons) and $Z=6$ (protons). The number of neutrons is $N = 14 - 6 = 8$.
3. Writing the Notation
Identify the element and write its chemical symbol $\text{X}$.
Determine the atomic number $Z$ (from the periodic table).
Determine the mass number $A$ (from the problem statement or by adding protons and neutrons).
Place $A$ as a superscript and $Z$ as a subscript to the left of $\text{X}$: $^{A}_{Z}\text{X}$.
4. Example Nuclides
Nuclide (symbol)
Element (X)
Atomic number (Z)
Mass number (A)
Neutrons (N = A‑Z)
Common use
$^{1}_{1}\text{H}$
H
1
1
0
Protium, hydrogen fuel
$^{2}_{1}\text{H}$
H
1
2
1
Deuterium, heavy water
$^{14}_{6}\text{C}$
C
6
14
8
Radiocarbon dating
$^{235}_{92}\text{U}$
U
92
235
143
Fissile material in reactors
$^{238}_{92}\text{U}$
U
92
238
146
Natural uranium, fertile material
5. Nuclide Notation in Nuclear Reactions
When writing nuclear equations, each reactant and product is expressed in nuclide notation. Conservation of mass number ($A$) and atomic number ($Z$) must be satisfied.