British scientist John Dalton begins using symbols to represent the atoms of different elements.

John Dalton’s introduction of **symbols to represent the atoms of different elements** was an important step in the development of modern chemistry. In the early nineteenth century, Dalton, an English chemist, physicist, and meteorologist, developed his atomic theory, arguing that matter was composed of extremely small particles called atoms. He proposed that the atoms of each element had their own characteristic properties and mass, while chemical compounds were formed when atoms of different elements combined in simple numerical ratios. To communicate these ideas more clearly, Dalton devised a system of visual symbols for representing individual elements and their atoms.

Dalton began using his atomic symbols in the early 1800s and published a systematic version of them in his influential book *A New System of Chemical Philosophy*, the first part of which appeared in **1808**. His symbols generally consisted of **circles containing different patterns, dots, lines, or letters**. For example, hydrogen was represented by a circle with a dot in its centre, oxygen by an empty circle, and carbon by a solid black circle. Other elements were given circles containing distinctive markings or initials. Dalton could then place these symbols together to illustrate compounds, providing a visual representation of how he believed atoms combined.

The system was closely connected with Dalton’s **atomic theory**. By arranging elemental symbols together, he attempted to show the number and type of atoms present in a compound. Although some of his proposed formulas were incorrect—for instance, he believed water consisted of one hydrogen atom and one oxygen atom rather than two hydrogen atoms and one oxygen atom—the underlying concept was revolutionary. Dalton’s notation encouraged chemists to think of chemical reactions as the rearrangement of identifiable atoms rather than simply as transformations of substances whose internal structure was unknown.

Dalton’s circular symbols were eventually replaced because they were cumbersome to draw and difficult to use for increasingly complicated compounds. In **1813–1814**, the Swedish chemist **Jöns Jacob Berzelius** introduced a much more practical system based on letters, generally using the first one or two letters of an element’s Latin or commonly used name. This became the foundation of the chemical notation still used today, such as **H for hydrogen, O for oxygen, and C for carbon**. Nevertheless, Dalton’s earlier system represented a major milestone: it was one of the first systematic attempts to give individual atoms a written identity and helped establish the symbolic language through which modern chemistry describes the composition of matter.