(P1) Topic 6- Radioactivity

Question 1

How much does the atomic number of a nucleus change by when an alpha particle is emitted

Answer 1

Down by 2

Question 2

How much does the mass number change by why an alpha particle is emitted

Answer 2

Goes down by 4

Question 3

What is a half-life of a radioactive isotope

Answer 3

The time taken for the number of undecayed nuclei to reduce by half
OR
The time take for the activity of the sample to reduce by half

Question 4

Isotopes have a different number of (?)

Answer 4

Neutrons

Question 5

Alpha particle

Answer 5

Made from: 2 protons and 2 neutrons
Symbol: α
Relative atomic mass: 4
Relative charge: +2
Ionisation: high
Range in air: very short (round 10cm)
Penetration charge: very short- can be stoped by thin paper

Question 6

Beta particle

Answer 6

Made from: a free electron that was made in the nucleus (a neutron to a proton)
Symbol: β- (e-)
Relative atomic mass: 1/1835
Relative charge: -1
Ionisation: moderate
Range in air: medium (about 1m)
Penetration: medium- stopped by a few m of aluminium

Question 7

Positron

Answer 7

Made from: exactly like an electron but the opposite charge (a proton to a neutron)
Symbol: β+ (e+)
Relative atomic mass: 1/1835
Relative charge: +1
Ionisation: likely to annihilate
Range in air: **
Penetration: **

Question 8

Gamma ray

Answer 8

Made from: a ray of pure energy (EM wave)
Symbol: γ
Relative atomic mass: 0
Relative charge: 0
Ionisation:low
Range in air: unlimited
Penetration: very long- stopped by multiple cm of lead or around a m of concrete

Question 9

What is Thompson’s plum pudding model

Answer 9

The scientific idea that an atom is a sphere of positive charge, with negatively charged electrons in it

Question 10

What did Rutherford expect to happen in his experiment

Answer 10

He expected the alpha particles to go straight through as according to Thompson’s plum pudding model there would be few obstacles so all of the alpha particles would go through the gold foil.