second page of notes

Question 1

Who calculated a charge to mass ratio for particles and proposed the ‘plum pudding’ model of the atom?

Answer 1

J.J. Thomson

Thomson’s model suggested that atoms consist of positive material with small negative particles (electrons) embedded within.

Question 2

What did Robert Millikan find about the mass of an electron in his oil drop experiment?

Answer 2

1837 times smaller than the smallest atom (hydrogen)

Millikan’s measurements provided a more accurate understanding of electron mass.

Question 3

What are the masses of protons, neutrons, and electrons?

Answer 3

• Proton (p+): 1.673 x 10^-24 g
• Neutron (no): 1.675 x 10^-24 g
• Electron (e−): 9.109 x 10^-28 g

These masses were calculated with improved accuracy later.

Question 4

What experiment did Ernest Rutherford conduct in 1911?

Answer 4

Bombarded thin gold foil with alpha particles

This experiment led to the discovery of the atomic nucleus.

Question 5

What did Rutherford conclude about the structure of the atom?

Answer 5

The center of an atom is dense and positive, most of the atom is empty space

He named the center the nucleus.

Question 6

What forces hold protons together in the nucleus despite their repulsion?

Answer 6

Nuclear forces

These are short-range attractive forces.

Question 7

Who discovered the neutron and what year was it discovered?

Answer 7

Irène and Frederic Joliot-Curie in 1932

The neutron was named by James Chadwick.

Question 8

What characteristics do waves have?

Answer 8

• Wavelength (λ)
• Amplitude (ψ)
• Frequency (f)

These properties are essential in understanding wave behavior.

Question 9

What is the equation that relates the speed of light, wavelength, and frequency?

Answer 9

c = λ f

Where c is the speed of light (299792458 m/s).

Question 10

What concept did Max Planck introduce regarding energy?

Answer 10

Atoms can gain or lose energy only in small, specific amounts called quanta

A quantum is the smallest amount of energy an atom can gain or lose.

Question 11

What phenomenon could not be explained by the wave model of light?

Answer 11

The photoelectric effect

This effect involves the liberation of electrons when light shines on a metal surface.

Question 12

In the photoelectric effect, what determines if electrons can be emitted from a metal surface?

Answer 12

The frequency of the light waves

A high enough frequency is necessary to liberate an electron.

Question 13

What is the kinetic energy of the emitted electron related to?

Answer 13

The frequency of the incoming light

Higher frequency light can liberate electrons with greater kinetic energy.