3.1 The History of the Atom

Question 1

What did Democritus discover?

Answer 1

he discovered the concept of the atom and predicted that matter is composed of elementary particles

Question 2

How long did it take for scientists to confirm Democritus’ theory?

Answer 2

2000 years

Question 3

Who was the first to apply stoichiometry?

Answer 3

Lavoisier

Question 4

What is Lavoisier also known as?

Answer 4

“Father of Modern Chemistry”

Question 5

Who created the modern atomic theory in 1807?

Answer 5

John Dalton

Question 6

What was stated in John Dalton’s atomic theory?

Answer 6

Elements consists of atoms
Atoms cannot be created divided or destroyed
Atoms of the same element have identical properties (like size and mass)

Question 7

What did J.J Thomson discover?

Answer 7

The electron and the mass to charge ratio of electrons

Question 8

What device did J.J Thomson use to discover the electron?

Answer 8

The cathode ray

Question 9

Who is associated with the “plum-pudding”/“raisin bun model”?

Answer 9

J.J Thomson

Question 10

Due to the fact that electrons could be generated using different metals as the electrodes means…

Answer 10

All atoms must contain electrons

Question 11

Since atoms are neutral they must contain…

Answer 11

A positive charge

Question 12

Who conducted the charged oil experiment?

Answer 12

Robert Millikan

Question 13

What was the outcome of the charged oil experiment?

Answer 13

Could slow the drops of oil by adjusting voltage

Question 14

What did Robert Millikan determine?

Answer 14

The mass of the electron

Question 15

What did Henri Becquerel discover?

Answer 15

That uranium could produce an image on a photogenic plate IN THE ABSENCE OF LIGHT

Question 16

What did Becquerel conclude about Uranium?

Answer 16

Uranium atoms must spontaneously emit radiation

Question 17

What is radioactivity?

Answer 17

The spontaneous decay of the nucleus of an atom

Question 18

What did Ernest Rutherford discover?

Answer 18

The alpha particle (which is essentially the helium atom)

Question 19

What else did Ernest Rutherford name?

Answer 19

The beta particle and the gamma ray

Question 20

What is the gold foil experiment?

Answer 20

Fired alpha particles at a thin sheet of gold foil

Question 21

What was the outcome and conclusions of the gold foil experiment?

Answer 21

MOST alpha particles passed through meaning atoms are mostly empty space
SOME alpha particles were scattered meaning there is a concentrated positive charge at the centre of the atom

Question 22

What was wrong with the gold foil experiment?

Answer 22

The observations did not support Thomson’s model

Question 23

What did Rutherford name positive charges as?

Answer 23

Protons

Question 24

Who is James Chadwick?

Answer 24

He worked with Rutherford to measure the mass of different nuclei

Question 25

What did Chadwick notice about the mass of the nuclei?

Answer 25

The mass of the nuclei was greater than the mass of the protons Also reasoned that the nucleus also contains uncharged particles called NEUTRONS

Question 26

What are isotopes?

Answer 26

Are atoms that have equal numbers of protons but different numbers of neutrons

Question 27

What are radioisotopes?

Answer 27

Unstable isotopes, their additional neutrons decay and release radiation

Question 28

What is the particle theory of light?

Answer 28

Light exists as a stream of light | Proposed by Greek philosophers in 300 BC

Question 29

Who created the wave theory of light?

Answer 29

Christiaan Huygens

Question 30

What is the wave theory of light?

Answer 30

Light exists as a wave | Supported by experiments on reflection, refraction and diffusion of light

Question 31

What theory fid Newton defend

Answer 31

The particle theory | Light is made up of tiny particles called corpuscles

Question 32

What did James Clerk Maxwell publish?

Answer 32

A Dynamical Theory of the Electromagnetic Field

Question 33

What is electromagnetism?

Answer 33

Light is on electromagnetic wave made of electric and magnetic fields, explaining how light could have an effect on charged particles

Question 34

Who first discovered the photoelectric effect?

Answer 34

Hertz

Question 35

What is the photoelectric effect?

Answer 35

a light shining on a metal surface (any surface) causes emissions of electrons from the metal/object

Question 36

What determines the energy of the electrons emitted from a substance?

Answer 36

Frequency

Question 37

What is the THRESHOLD FREQUENCY?

Answer 37

The minimum frequency required to emit an electron

Question 38

What are blackbodies?

Answer 38

Objects that can be heated to incandescence, perfect emitters and absorbers, do not reflect light

Question 39

Who worked with blackbodies?

Answer 39

Max Planck

Question 40

What does the Classical Theory (Rayleigh-Jeans Law) predict?

Answer 40

Increasing temperature will result in objects emitting infinitely high intensity UV light

Question 41

What did Planck conclude about energy?

Answer 41

Energy must be quantized (gained or lost in very small packets) NOT as a continuous wave