The Development of the Modern Model of the Atom

The video explores the development of the atomic model, starting with Democritus' ancient theory of indivisible atoms. It progresses to J.J. Thomson's discovery of the electron using cathode rays, leading to the plum pudding model. Rutherford's gold foil experiment reveals the nuclear model with a dense nucleus. Bohr refines this by introducing electron shells with specific energy levels. Finally, Chadwick discovers the neutron, explaining discrepancies in atomic mass.

What was Democritus' main contribution to the concept of matter?

• He developed the plum pudding model.

• He proposed that matter is made of indivisible particles called atoms.

• He discovered the neutron.

• He discovered the electron.

What did J.J. Thomson's cathode ray experiment demonstrate?

• The existence of neutrons.

• The existence of a positively charged nucleus.

• The presence of negatively charged particles, later called electrons.

• The indivisibility of atoms.

What was the key finding from Rutherford's gold foil experiment?

• Atoms are indivisible.

• Electrons are embedded in a positively charged mass.

• Neutrons are present in the nucleus.

• Atoms are mostly empty space with a dense, positively charged nucleus.

How did Neils Bohr modify Rutherford's atomic model?

• By introducing the concept of electron shells with specific energy levels.

• By discovering the neutron.

• By proposing the plum pudding model.

• By suggesting that atoms are indivisible.

Who discovered the neutron and when?

• Neils Bohr in 1913.

• James Chadwick in 1932.

• Ernest Rutherford in 1911.

• J.J. Thomson in 1897.

What problem did the discovery of the neutron solve?

• The presence of a positively charged nucleus.

• The indivisibility of atoms.

• The discrepancy in the mass of heavier elements compared to their protons.

• The existence of electron shells.

What did further alpha scattering experiments reveal about hydrogen?

• Its charge is shared between a whole number of smaller particles.

• It has the most charge of any element.

• It has no nucleus.

• It is composed entirely of neutrons.