[Unit 1.1] | Fundamental Particles

Question 1

What did the Greeks believe matter was made from?

Answer 1

Small indivisble spheres - atoms.

Question 2

In 1661, who proposed that there are substances that cannot be simplified, called elements?

Answer 2

Boyle

Question 3

What did Dalton propose in 1803?

Answer 3

• He believed elements were made of invsible spheres which could not be broken down.
• He also suggested that atoms of different elements have different masses.

Question 4

In 1896 Becquerel discovered radioactivity, what did this suggest?

Answer 4

It showed that particles could be emitted from atoms, suggesting they were not indivisible.

Question 5

What did Thomson’s 1897 model of the atom consist of?

Answer 5

It is called the plum pudding model, and consists of a postively charged sphere with negative clouds of electrons dotted throughout.

Question 6

What conclusion did the alpha foil experiment of 1911 come to?

Answer 6

• Rutherford discovered a positive nucleus at the centre of the atom where mass is concentrated.
• This led him to believe the atom is mostly empty space.

Question 7

What change occured to the model of the atom in 1913?

Answer 7

Bohr discovered fixed orbits around the nucleus.

Question 8

When did Chadwick discover protons and neutrons?

Answer 8

1932.

Question 9

What are the relative masses and charges of the 3 fundamental particles (electrons, neutrons and protons)?

Answer 9

Relative Masses:
• Electron: 1/1800
• Neutron: 1
• Proton: 1

Relative Charges:
• Electron: -1
• Neutron: 0
• Proton: 1

Question 10

What force holds the nucleons together?

Answer 10

Strong nuclear force, which overcomes the electrostatic attraction between protons and electrons and also prevents protons from repelling one another.