5.1- Early models of the atom - Dalton to Rutherford

Question 1

What is atomism?

Answer 1

the proposition that a sample of solid matter could be cut into smaller pieces until there was a piece that you could no longer cut up.

Question 2

Who developed the theory of atomism?

Answer 2

Leucippus and Democritus, ancient greeks.

Question 3

Democritus called the smallest/indivisible particles of matter what?

Answer 3

Atomos, surrounded by empty space.

Question 4

Who said “Nothing exists except atoms and empty space, everything else is opinion.”

Answer 4

Democritus.

Question 5

Aristotle made what proposition after the development of atomism?

Answer 5

Alchemy: matter is made of earth, water air and fire.

Question 6

Robert boyle defined elements as what?

Answer 6

A single substance that could not be broken down anymore.

Question 7

What is John Dalton’s atomic theory?

Answer 7

1. matter is composed of tiny particles called atoms which cannot be broken/created/destroyed.
2. Element’s atoms are identical, diff. from another elements’.
3. Atoms of diff. elements. combine in specific ratios to form compounds.
4. In a chem reaction, atoms separate/rearrange/combine to form new compounds.

Question 8

Describe crooke’s tube.

Answer 8

a glass tube with two electrodes, a negative cathode on one end and positive anode halfway, a flat cross two thirds of the way along it.

Question 9

What did crooke’s tube do?

Answer 9

Showed the presence of cathode rays, made up of charged particles.

Question 10

Who discovered that cathode rays are made up of streams of negatively charged particles?

Answer 10

JJ Thompson.

Question 11

What discovery did JJ Thompson make as a result of determining the charge to mass ratio of the cathode ray particles?

Answer 11

He discovered that cathode rays are made up of negatively charged particles who are subatomic in size, smaller than an atom, and exist in all elements.

Question 12

Who discovered the electron?

Answer 12

JJ Thompson.

Question 13

What do you call a negatively charged subatomic particle found within all atoms?

Answer 13

Electron.

Question 14

What is the plum pudding model?

Answer 14

JJ Thompson’s model showing an atome made up of negatively charged electrons embedded in a positively charged material.

Question 15

Who named 3 types of radioactivity and what were they?

Answer 15

Ernest Rutherford: Alpha Decay, Beta Decay, Gamma Decay.

Question 16

Rutherford discovered what type of radioactivity?

Answer 16

Alpha Decay.

Question 17

The alpha particles produced by Rutherford’s alpha decay were really what?

Answer 17

nuclei of helium atoms.

Question 18

What are the three basic componenets of rutherford’s gold foil experiments.

Answer 18

• Alpha particle source
• Fluorescent screen
• Gold foil.

Question 19

What did rutherford’s gold foil experiments find out about alpha particles compared to electron particles?

Answer 19

• Alpha particles are 7000-8000 times bigger than electrons.

- They travel really fast.

Question 20

What were the results of rutherford’s gold foil experiments?

Answer 20

Some alpha particles passed through the foil, some passed through but deflected off their straight path, some bounced off the foil and rebounded towards the source.

Question 21

Who said “It was almost as incredible as if you fired a 15 inch shell at a piece of tissue paper and it came back and hit you.”

Answer 21

Ernest Rutherford.

Question 22

What is coulomb’s law?

Answer 22

Electrostatic force is inversely proportional to charge separation or density- as charge spreads out, the force it can apply gets weaker.

Question 23

What do you call the tiny, dense concentration of positive charge at the centre of an atom, and who proposed it?

Answer 23

The nucleus, Ernest Rutherford.

Question 24

What new model of the atom did rutherford propose?

Answer 24

• The nucleus represented most of the atom’s mass, but little of its volume.
• The electrons outside of the nucleus represented most of the atom’s volume but very little of its mass.

Question 25

What do you call the positively charged massive particle found in an atom’s nucleus and who discovered it?

Answer 25

-Proton, Ernest Rutherford.

Question 26

What do you call the neutral particle found in an atom’s nucleus, whose mass is slightly more than a proton’s, and who discovered it?

Answer 26

-Neutron, Ernest Rutherford.

Question 27

What do you call the whole number representing the number of protons in a nucleus, the charge, and the number of electrons in a neutral atom?

Answer 27

The atomic number (Z).