Radioactivity

Question 1

Radioactive decay

Answer 1

Caused by unstable atoms. The nucleus decays and emits radioactive radiation

Question 2

Type of radiation

Answer 2

Alpha, Beta, Gamma

Question 3

Alpha

Answer 3

Alpha is 2 protons and 2 neutrons
Range in air - Up to 5cm
Absorbed by - Paper
Ionisation power - Very ionising

Question 4

Beta

Answer 4

Beta is an electron from the nucleus
Range in air - Up to 1m
Absorbed by - A few mm of aluminium
Ionisation power - Quite ionising

Question 5

Gamma

Answer 5

Gamma is an Electromagnetic radiation wave
Range in air - A long way
Absorbed by - Thick lead
Ionisation power - Weakly ionising

Question 6

Decay equations

Answer 6

Elements are written
z
X
a

Z =  mass number (number of protons and neutrons)
A = atomic number (number of protons)
X = element symbol

Question 7

Alpha decay

Answer 7

222 4
Ra —–> He + Rn
88 2
The proton an atomic mass numbers on both sides of these equations add up to the same numbers.

These equations are then balanced.
208 4
Po —–> He + Pb
84 2

Question 8

Beta decay

Answer 8

14 0
C —-> N + E
6 -1
The proton an atomic mass numbers on both sides of these equations add up to the same numbers.

These equations are then balanced.
31 0
I —–> Xe + E
53 -1

Question 9

Rutherford’s scattering experiment

Answer 9

Result =
Most alpha went straight through.
Some alpha had small deflection.
A few alpha turned back

Conclusion =
The atom is mostly empty space
The nucleus had a positive charge
The nucleus contained most of the mass of the atom