Thomson realized that cathode rays could be made up of only one kind of particle if he was able to deflect them using an electric field without changing their properties, which was possible with a magnet.

Thomson concluded that the glowing particles were not simply light, but had mass because they were deflected in opposite directions by an electrical field.

He noticed that the tube gave off a green glow as cathode rays hit the opposite electrode. Thomson entered a modified Crookes tube into an electrical field. Thomson discovered that an atom consists of a heavy and dense core, known as the nucleus, which is orbited by much lighter particles: protons and electrons. In a world-shattering discovery, English physicist J.J Thomson disproved the idea that atoms are indivisible. Charcoal, graphite, and diamond have many differences in properties from one another despite having similar structures which suggest there may exist an underlying explanation as to why this happens.

Finally, allotropes are a poorly explained phenomenon that cannot be accounted for by Dalton's theory.

For example, chlorine has two isotopes: one at mass number 35 and another at 37. Isotopes are atoms with different masses, which goes against Dalton's original theory.

Atoms of the same element typically will have similar properties as Dalton proposed.

This means Dalton's theory of atoms of different elements being different in all respects was incorrect in certain cases. In the case of these two elements, they share a 40 amu atomic mass.

Dalton's theories were also wrong when it came to, for example, calcium and argon.

In contrast, complex organic compounds like sugar (C 12H 22O 11) defy this theory.

Dalton also proposed that atoms of different elements combine in simple whole-number ratios such as 2:3 or 3:5 for Hydrogen and Oxygen respectively.

The indivisibility of an atom is no longer accepted, as it was discovered that atoms can be further divided into protons, neutrons, and electrons. Despite this, many of his ideas became the foundation for discoveries in chemistry in the coming decades. While Dalton was considered a pioneer of modern chemistry, some of his theories were later proven inaccurate.

In a chemical reaction, atoms are rearranged, separated, or recombined to form new compounds but no atom is created or destroyed.

The resulting particle is called a molecule.

Chemical compounds are made up of at least 2 atoms of different elements.

Atoms of different elements vary in size, mass, and chemical behavior.

All atoms of the same element are identical and have the same mass.Matter is made up of atoms, small and indivisible particles.What are the 5 Points of Dalton's Atomic Theory?ĭalton's Atomic Theory was formulated by John Dalton in 1808, and it remains a fundamental tenet of chemistry to this day.

Who made the atomic theory