nuclear + particle physics

Question 1

describe the Thomson model of the atom

Answer 1

• plum pudding model

- atoms made up of a sphere of positive charge with electrons sprinkled in it

Question 2

describe Rutherford’s experiment

Answer 2

• stream of alpha particles from radioactive source fired at very thin gold foil
• particles strike a fluorescent screen, a tiny visible flash of light is produced
• flashes recorded and counted at different angles

Question 3

what did Rutherford observe from his experiment?

Answer 3

observed that most alpha particles went straight through the foil, but a few scattered at angles greater than 90

Question 4

what conclusions can be made from alpha particle scattering experiment?

Answer 4

• atom is mainly empty space
• some particles deflected at right angles, so centre must be a large positive charge- nucleus
• few particles were deflected at more than 90 degrees, so nucleus is tiny
• mass and positive charge in atom must be contained in a tiny central nucleus

Question 5

describe the nuclear model of the atom

Answer 5

inside every atom, there is a nucleus of protons and neutrons which is positively charged. electrons orbit the nucleus
size of nucleus is 1/10000 of the whole atom

Question 6

what are protons and neutrons also called?

Answer 6

nucleons

Question 7

what is the proton number and the symbol?

Answer 7

number of protons in the nucleus

symbol- Z

Question 8

what is the nucleon number and the symbol?

Answer 8

total number of protons and neutrons

symbol- A

Question 9

what is the mass of a proton/neutron?

Answer 9

1 atomic unit = 1.661 x 10^-27

Question 10

define an isotope

Answer 10

same proton number, different nucleon number

can be radioactive due to unstable nuclei

Question 11

what does a change to the number of neutrons affect?

Answer 11

the stability of the nucleus