Atomic Theory Timeline

Who was the philosopher that first proposed the idea of indivisible matter?

Democritus, who named the smallest piece of matter 'atomos'.

What four elements did Aristotle believe all matter was made of?

Fire, air, water, and earth.

What was the impact of Aristotle's ideas on the field of chemistry?

His ideas dominated for nearly 2000 years, hindering scientific progress.

What did John Dalton contribute to atomic theory in 1803?

He proposed that all matter is made of atoms, which are indivisible and indestructible.

What analogy did Dalton use to describe atoms?

The billiard ball analogy, suggesting atoms are solid and indivisible.

What discovery did J.J. Thomson make in 1897?

He discovered the electron, indicating that atoms are made of smaller particles.

What model of the atom did J.J. Thomson propose?

The 'plum pudding' model, where electrons are scattered in a positively charged substance.

What experiment did Ernest Rutherford conduct in 1908?

He fired positively charged particles at gold foil, leading to the discovery of the nucleus.

What did Rutherford conclude about the structure of the atom?

Atoms have a small, dense, positively charged nucleus surrounded by mostly empty space.

What atomic model did Niels Bohr propose in 1913?

He proposed that electrons move in definite orbits around the nucleus, similar to planets around the sun.

What analogy did Bohr use for his atomic model?

The solar system analogy, where electrons orbit the nucleus at specific distances.

What is the modern atomic theory developed in the 20th century?

Electrons move in an electron cloud around the nucleus, not in fixed orbits.

Who were some of the scientists that contributed to the modern cloud theory?

Schrodinger, Heisenberg, and Einstein, among others.

What analogy is used to describe the electron cloud in modern atomic theory?

The cotton ball analogy, representing the diffuse nature of the electron cloud.

What does the electron cloud theory suggest about electron movement?

Electrons whirl around the nucleus at high speeds, with their location depending on energy levels.

What was the significance of Dalton's atomic theory?

It marked the acceptance of the concept of atoms after a long period of neglect in chemistry.

How did Rutherford's findings change the understanding of atomic structure?

He established that atoms contain a nucleus, fundamentally altering the atomic model.

What did the 'plum pudding' model fail to explain?

It did not account for the existence of a dense nucleus within the atom.

Why is the atomic theory considered to build on past research?

Each new model and theory has evolved from previous ideas and discoveries.

What was the main idea behind Democritus's atomic theory?

Matter could be divided until reaching the smallest indivisible particle, the atom.

What did Aristotle add to the understanding of matter despite being incorrect?

He provided a framework of elements and properties that influenced thought for centuries.