1. Alpha, Beta, Gamma Radiation
Chapter 19
Alpha, Beta, Gamma Radiation

2. The Atom The atom consists of two parts:
1. The nucleus which contains:
protons
neutrons
2. Orbiting electrons.

3. The Atom
All matter is made up of elements (e.g. carbon, hydrogen, etc.).
The smallest part of an element is called an atom.
Atom of different elements contain different numbers of protons.
The mass of an atom is almost entirely due to the number of protons and neutrons.

4. X A Z Mass number = number of protons + number of neutrons
Element symbol Z
Atomic number
= number of protons

5. U U 235 92 238 92 There are many types of uranium: A Z
Number of protons
Number of neutrons A Z
Number of protons
Number of neutrons

6. U U 235 92 238 92 There are many types of uranium: A 235 Z 92
Number of protons
Number of neutrons
143 A
238 Z 92
Number of protons
Number of neutrons
146

7. Definition of Isotope
Isotopes of any particular element contain the same number of protons, but different numbers of neutrons.

8. Radioactivity
The process by which certain elements emit particular forms of radiation.
Radioactivity is the process of emitting such forms of radiation.
There are 3 major forms of emitted radiation: alpha, beta, and gamma radiation.

9. Alpha Radiation
Alpha particles are fast- flying positively charged subatomic particles
Combination of 2 protons and 2 neutrons (nucleus of a Helium atom)... Alpha Radiation

11. Alpha Decay
An alpha particle is identical to that of a helium nucleus.
It contains two protons and two neutrons.

12. Alpha Decay Rn
222 86 He 4 2 Ra
226 88

13. X Y + He Alpha Decay A Z A - 4 Z - 2 4 2 unstable atom (parent)
alpha particle
(radiation)
more stable atom
(daughter)

14. Alpha Decay X A Z Y
A - 4
Z - 2 + He 4 2 Ra
226 88 Rn
222 86 + He 4 2

15. Beta radiation
Beta particles are fast- flying negatively charged subatomic particles.
One electron that is ejected by an atom... Beta Radiation

16. Beta Decay
When a nucleus has too many neutrons, it tends to beta decay.
When beta decay occurs a neutron within the nucleus emits the particle and changes into a proton.
The proton number increases but the mass number stays the same
only now you have one more proton and one less neutron!
The resulting daughter nucleus is of an element 1 position to the right

17. Beta Decay
As a result of beta decay, the nucleus has one less neutron, but one extra proton.
The atomic number, Z, increases by 1 and the mass number, A, stays the same.

18. Beta Decay b -1 At
218 85 Po
218 84

19. Beta Decay X A Z Y
Z + 1 + b -1 Po
218 84 Rn 85 + b -1

20. Beta Decay Th
234 90 Y A Z + b -1 Th
234 90 Pa 91 + b -1

21. Gamma radiation
Gamma radiation is an extremely energetic form of electromagnetic radiation.
Located to the far end of the electromagnetic spectrum and has a much higher energy than visible light.
No electrical charge or mass.

22. Gamma Decay
Gamma rays are not charged particles like a and b particles.
Gamma rays are electromagnetic radiation with high frequency.
When atoms decay by emitting a or b particles to form a new atom, the nuclei of the new atom formed may still have too much energy to be completely stable.

23. Penetrating Power of Radiation

27. Transmutations, Half-Lives, and Carbon Dating
Chapter
Transmutations, Half-Lives, and Carbon Dating

28. Transmutations
When a nucleus ejects an alpha or beta particle, the atomic number is changed, so the element changes.
This is called a transmutation.
When this change occurs, energy is released in the form of gamma radiation and kinetic energy.

30. Alpha decay
When an alpha particle is ejected, 2 protons and 2 neutrons are lost
Mass Number decreases by 4
Atomic Number decreases by 2

31. Beta Decay
A beta particle is an electron emitted by a neutron, as the neutron transforms to a proton
Beta emission leaves the element with 1 fewer neutron and 1 more proton
Mass remains the same
Atomic Number increases by 1

32. Half-Lives
Half-life: measurement of radioactive decay rate. The amount of time needed for 1/2 the radioactive atoms to decay
Half-lives are constant- not affected by the environment
The shorter the half-life of a substance, the more radioactive it is

33. What is the half-life of cesium?

34. if you have a sample of a radioactive isotope that has a half-life of one day, how much of the original sample will remain at the end of the second day? third day?

35. Answer!
At the end of two days, 1/4 of the original sample is left- one-half disappears by the end of the first day, and one-half of that disappears by the end of the second day (1/2 x 1/2= 1/4)
At the end of three days, one-eighth (1/8) of the original sample remains

36. What becomes of the decayed atoms of the sample?

37. The atoms that decay are now atoms of a different element!
Answer!