Key Discoveries in Chemistry

Antoine Lavoisier is recognised as the father of modern chemistry. He thought that the existence of atoms was philosophically impossible.

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In 1803, the scientist John Dalton proposed “the new atomic theory”, stating that all matter is made up of small indivisible particles called atoms, which he explained through the following statements:

• Matter is made up of very small particles called atoms, which cannot be destroyed or broken down further.

• Atoms of the same element have the same mass and properties.

• Atoms of different elements have different masses and different properties.

• Chemical compounds form when atoms of two or more different elements join.

• Atoms of different elements can combine in different proportions to form a variety of substances.

We now know that the first two statements of Dalton’s theory are not entirely true. However, this theory was the basis for the scientific contributions of other atomic models:

Today, we know the following facts about atoms:

• They are made up of electrons, protons and neutrons.

• Atoms of an element have the same number of protons and electrons but can have different numbers of neutrons.

• Atoms of different elements have different numbers of protons and electrons.