Atomic Models Through the Lens of Early Experiments

The video discusses early atomic models, starting with Thomson's model, which proposed that positive charge is uniformly distributed in an atom with electrons embedded like seeds in a watermelon. However, this model couldn't explain atomic stability and mass. Rutherford's experiments with alpha particles revealed that atoms have a small, dense nucleus, leading to his atomic model. This model described a central nucleus with electrons orbiting it, but it couldn't account for atomic stability as per electromagnetic theory.

What analogy did Thomson use to describe his atomic model?

• A watermelon with seeds

• A plum pudding

• A solar system

• A cloud of electrons

What did Lennard conclude about the structure of the atom from his cathode ray experiments?

• Atoms consist mostly of empty space

• Atoms are made of only electrons

• Atoms have a dense nucleus

• Atoms are solid throughout

What did Lennard fail to explain in his atomic model?

• How particles are held in the atom

• The existence of neutrons

• The presence of electrons

• The distribution of positive charge

What was the main observation from Rutherford's gold foil experiment?

• Alpha particles were attracted to the nucleus

• Alpha particles were deflected at 90 degrees

• Most alpha particles passed through undeflected

• All alpha particles were absorbed

What did Rutherford propose about the structure of the atom based on his experiments?

• Atoms are made of only electrons

• Atoms have no empty space

• Atoms have a central nucleus

• Atoms are indivisible

What is the approximate radius of the nucleus according to Rutherford's calculations?

• 2.4 meters

• 2.4 quadrillionth meters

• 2.4 millimeters

• 2.4 nanometers

What did Rutherford identify as the cause of large angle deflections of alpha particles?

• Magnetic forces

• Gravitational forces

• Nuclear forces

• Electric repulsive forces from the nucleus

What did Rutherford's model suggest about the distribution of mass in an atom?

• Mass is negligible

• Mass is located in the electron cloud

• Mass is concentrated in the nucleus

• Mass is evenly distributed

Why did Rutherford's model fail to explain atomic stability?

• It did not include protons

• It assumed atoms were solid

• It suggested electrons should spiral into the nucleus

• It did not account for the mass of electrons

According to electromagnetic theory, what should happen to electrons in Rutherford's model?

• They should repel each other

• They should radiate energy and collapse into the nucleus

• They should remain stationary

• They should orbit indefinitely without energy loss