From Dalton's Circles to Berzelius's Letters

Introduction

The neat letters H, O and Fe that fill chemistry books today were not always used. For centuries, people who studied materials drew pictures and secret signs. In the early nineteenth century two scientists changed this: John Dalton drew elements as circles, and Jöns Jacob Berzelius replaced the circles with letters. Tracing this history shows why our present system is so practical and why it has lasted for more than two hundred years.

Core explanation

Alchemical signs. Medieval and early modern alchemists linked the seven metals they knew with the Sun, Moon and planets. Gold was shown by a circle with a dot (the Sun), silver by a crescent (the Moon), and iron by the sign of Mars. These signs were often kept deliberately mysterious, and different writers used different signs for the same material. They could not show how substances were built up.

Lavoisier's reforms. In the 1780s Antoine Lavoisier and colleagues introduced a systematic set of names for elements and compounds, such as "oxygen" and "hydrogen". This made names logical, but there was still no good shorthand for writing them.

Dalton's circles. Around 1808 , John Dalton published his atomic theory , which said each element is made of its own kind of atom. To show this he drew each atom as a small circle with a distinctive marking:

Element Dalton's sign --- --- Hydrogen circle with a dot in the centre Oxygen plain empty circle Carbon solid black circle Sulfur circle with a cross Metals circle with a capital letter inside, e.g. C for copper

Compounds were drawn by placing circles side by side, which for the first time showed atoms combining . However, the pictures were slow to draw, hard to print and easy to confuse, and there were not enough distinct markings for all the elements being discovered.

Berzelius's letters. In 1813–1814 the Swedish chemist Jöns Jacob Berzelius proposed using letters instead. Each element would be represented by the first letter of its Latin (or Latinised) name, with a second letter added when two names began with the same letter: C for carbon, Ca for calcium, Cl for chlorine. Letters could be printed with ordinary type, written quickly and understood easily. Berzelius also wrote numbers to show how many atoms were combined — originally as superscripts, such as H²O, while today we use subscripts, H₂O.

Resistance and acceptance. Dalton disliked the letters and continued to use his circles, but the letters were so practical that they spread across Europe within a few decades. Today's IUPAC symbols are a direct descendant of Berzelius's system.

Step-by-step reasoning

How the representation of elements improved:

1. Alchemists used secret, inconsistent pictorial signs for a few metals. 2. Lavoisier made the names of substances systematic. 3. Dalton linked each element to one kind of atom and drew atoms as circles. 4. Berzelius replaced circles with letters based on Latin names, adding numbers for atom counts. 5. International agreement fixed the symbols we use now.

Visual explanation

Imagine writing water three ways: an alchemical sign for water (a downward triangle), Dalton's picture of a dotted circle beside an empty circle, and Berzelius-style H₂O. Only the last is quick to write and tells you the atom ratio clearly.

Real-world analogy

The change from pictures to letters is like the change from hieroglyphs to an alphabet. Picture-writing needs many unique images and skilled artists; an alphabet uses a small set of letters that anyone can combine and print.

Real-world example

Dalton's original wooden models and his printed charts of atomic symbols are kept in museum collections in Manchester, where he worked. Visitors can compare them with a modern periodic table and see how much more compact Berzelius's letters are.

Why?

Why did letters win? They could be set with the ordinary metal type used by printers, they did not need drawing skills, they could be extended to any number of new elements, and they linked each symbol to the element's name, making them easy to remember.

Common misconception

"Dalton invented the chemical symbols we use today." Dalton introduced atomic symbols as circles, which was important for atomic theory, but the letter symbols we use come from Berzelius.

Worked example

Question: Dalton drew a compound as one solid black circle joined to one plain circle. Using modern symbols, what would this be?

Reasoning: In Dalton's system the solid black circle is carbon and the plain circle is oxygen. One carbon atom joined to one oxygen atom is written CO today.

Answer: CO, carbon monoxide (Dalton called it "carbonic oxide").

Quick check

1. Which scientist introduced letter-based chemical symbols? Answer: Jöns Jacob Berzelius, in 1813–1814.

Exam focus

Be able to compare Dalton's and Berzelius's systems: Dalton used circles to show atoms, while Berzelius used letters from Latin names. State why letters are better: easier to write and print, and easy to extend to new elements.

Advanced insight

Dalton's pictures sometimes gave wrong formulae: he assumed the simplest ratio, so he drew water as one hydrogen and one oxygen atom (HO). The correct formula, H₂O, became accepted only after work on combining volumes of gases by Gay-Lussac and Avogadro was understood later in the century.

Summary

Alchemists used secretive signs for a few metals. Lavoisier made names systematic. Around 1808 Dalton drew each kind of atom as a marked circle, showing atoms combining. In 1813–1814 Berzelius introduced letter symbols from Latin names, with numbers for atom counts. Letters were quicker, printable and extendable, and they became today's symbols.

Practice questions

1. What did John Dalton use to represent atoms of elements? Answer: Small circles with different markings, one design for each element. 2. Give two advantages of Berzelius's letters over Dalton's circles. Answer: They were quicker to write and could be printed with ordinary type; they could easily be extended to new elements. 3. Why does calcium have the symbol Ca rather than just C? Answer: C was already used for carbon, so a second letter was added to tell them apart. 4. How did alchemical signs differ from modern symbols? Answer: They were pictorial, often secret and inconsistent, covered only a few substances and could not show how atoms combine.