1. Why do some atoms undergo nuclear changes?
NUCLEAR CHEMISTRY
Why do some atoms undergo nuclear changes?

2. ATOMIC COMPOSITION Protons + electrical charge
mass = x g
relative mass = atomic mass units (amu)
Electrons
negative electrical charge
relative mass = amu
Neutrons
no electrical charge
mass = amu

3. Radioactivity
One of the pieces of evidence for the fact that atoms are made of smaller particles came from the work of Marie Curie ( ).
She discovered radioactivity, the spontaneous disintegration of some elements into smaller pieces.

4. Radioactivity
Emission of particles and/or energy due to a change in the nucleus of an atom.
Nuclear Radiation also called Ionizing radiation
Measure with Geiger Counter

5. Geiger Counter:
Radiation detection

6. Isotopes Hydrogen: Helium, 42He Lithium, 63Li and 73Li
11H, protium
21H, deuterium
31H, tritium (radioactive)
Helium, 42He
Lithium, 63Li and 73Li
Boron, 105B and 115B
Except for 11H the mass number is always at least 2 x atomic number.
Repulsive forces between protons must be moderated by neutrons.

7. Isotopes Boron-10 has 5 p and 5 n: 105B Boron-11 has 5 p and 6 n: 115B
Same element (Z) but different mass number (A).
Boron-10 has 5 p and 5 n: B
Boron-11 has 5 p and 6 n: B

8. Why do unstable isotopes undergo nuclear reactions?
Unstable isotopes undergo nuclear reactions so that they may be changed, or transformed, into stable isotopes.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

9. Stability of Nuclei
Heaviest naturally occurring non-radioactive isotope is 209Bi with 83 protons and 126 neutrons
There are 83 x 126 = 10,458 possible isotopes. Why so few actually exist?

10. Band of Stability and Radioactive Decay
Isotopes with a n/p ratio, below or above the band of stability decay, by various nuclear reactions.

11. Stability of Nuclei Out of > 300 stable isotopes: N Even Odd Z 15752
3115P
Even
Odd 50 5
21H, 63Li, 105B, 147N, 18073Ta
199F

12. What are three types of nuclear radiation?
Types of Radiation
Types of Radiation
What are three types of nuclear radiation?
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

13. Radiation is emitted during radioactive decay.
Types of Radiation
Radiation is emitted during radioactive decay.
Three types of nuclear radiation are alpha radiation, beta radiation, and gamma radiation.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

14. Types of NUCLEAR Radiation

15. Types of Radiation
Alpha Radiation
Some radioactive sources emit helium nuclei, which are also called alpha particles.
Each alpha particle contains two protons and two neutrons and has a double positive charge.
An alpha particle is written He or a. 4 2
The electric charge is usually omitted.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

16. Alpha Radiation U
238 92
Uranium-238
Th +
234 90
Thorium-234
He (a emission) 4 2
Alpha particle
Radioactive
decay
The radioisotope uranium-238 emits alpha radiation and is transformed into another radioisotope, thorium-234.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

17. Alpha Radiation U Th + He →
When an atom loses an alpha particle, the atomic number of the product is lowered by two and its mass number is lowered by four. U
238 92
Th +
234 90 He 4 2 →
In a balanced nuclear equation, the sum of the mass numbers (superscripts) on the right must equal the sum on the left.
The same is true for the atomic numbers (subscripts).
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

18. Alpha Radiation
Because of their large mass and charge, alpha particles do not travel very far and are not very penetrating.
A sheet of paper or the surface of your skin can stop them.
But radioisotopes that emit alpha particles can cause harm when ingested.
Once inside the body, the particles don’t have to travel far to penetrate soft tissue.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

19. Beta Radiation
An electron resulting from the breaking apart of a neutron in an atom is called a beta particle.
The neutron breaks apart into a proton, which remains in the nucleus, and a fast-moving electron, which is released. n 1
Neutron
p +
Proton e –1
Electron
(beta particle) →
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

20. The –1 represents the charge on the electron.
Beta Radiation n 1
Neutron
p +
Proton e –1
Electron
(beta particle) →
The –1 represents the charge on the electron.
The 0 represents the extremely small mass of the electron compared to the mass of a proton.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

21. Beta Radiation C N + e (b emission) →14 6
Carbon-14 (radioactive)
N + 7
Nitrogen-14 (stable)
e (b emission) –1
Beta particle →
The nitrogen-14 atom has the same mass number as carbon-14, but its atomic number has increased by 1.
It contains an additional proton and one fewer neutron.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

22. Thus, beta particles are more penetrating than alpha particles.
Beta Radiation
A beta particle has less charge than an alpha particle and much less mass than an alpha particle.
Thus, beta particles are more penetrating than alpha particles.
Beta particles can pass through paper but are stopped by aluminum foil or thin pieces of wood.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

23. Beta Radiation
Because of their opposite charges, alpha and beta radiation can be separated by an electric field.
Alpha particles move toward the negative plate.
Beta particles move toward the positive plate.
Gamma rays are not deflected.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

24. Gamma Radiation
A high-energy photon emitted by a radioisotope is called a gamma ray.
The high-energy photons are a form of electromagnetic radiation.
Gamma rays are emitted during radioactive decay.
Ra +
226 88
Radium-226 Th
230 90
Thorium-230
He + g 4 2
Alpha particle
Gamma ray →
Pa +
234 91
Protactinium-234 Th 90
Thorium-234
e + g –1
Beta particle
Gamma ray →
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

25. Gamma rays have no mass and no electrical charge.
Types of Radiation
Gamma Radiation
Gamma rays have no mass and no electrical charge.
Emission of gamma radiation does not alter the atomic number or mass number of an atom.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

26. Gamma rays are extremely penetrating making them dangerous.
Gamma Radiation
Gamma rays are extremely penetrating making them dangerous.
Gamma rays pass easily through paper, wood, and the human body.
They can be stopped, although not completely, by several meters of concrete or several centimeters of lead.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

27. Penetrating Ability

28. CHEMISTRY & YOU
Gamma rays can be dangerous because of their penetrating power. What property determines the relative penetrating power of electromagnetic radiation?
The wavelength and energy of electromagnetic radiation determine its relative penetrating power. Gamma rays have a shorter wavelength and higher energy than X-rays or visible light.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

29. Characteristics of Some Types of Radiation
Interpret Data
Characteristics of Some Types of Radiation
Type
Consists of
Symbol
Charge
Mass (amu)
Common source
Penetrating power
Alpha radiation
Alpha particles (helium nuclei) a, 2+ 4
Radium-226
Low (0.05 mm body tissue)
Beta radiation
Beta particles (electrons) b, 1–
1/1837
Carbon-14
Moderate
(4 mm body tissue)
Gamma radiation
High-energy electromagnetic radiation g
Cobalt-60
Very high (penetrates body easily) He 4 2 e –1
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

30. Which process involves a radioactive nucleus releasing a high-speed electron?
A. oxidation
B. alpha emission
C. beta emission
D. gamma radiation C
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

31. How do nuclear reactions differ from chemical reactions?
Radioactivity
How do nuclear reactions differ from chemical reactions?
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

32. Radioactivity
Unlike chemical reactions, nuclear reactions are NOT affected by changes in temperature, pressure, or the presence of catalysts.
Nuclear reactions of a given radioisotope cannot be slowed down, sped up, or stopped.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

33. Nuclear Reactions
Ernest Rutherford found Ra forms Rn gas when emitting an alpha particle.
1902—Rutherford and Soddy proposed radioactivity is the result of the natural change of the isotope of one element into an isotope of a different element.

34. Nuclear Reactions orTransmutations
Natural Decay
Spontaneous breakdown of unstable nuclei.
Called Radioisotopes

35. NATURAL Decay:
DECAY = Fall apart
Alpha DECAY
Beta DECAY
Positon DECAY

36. If the product of a nuclear reaction is unstable, it will decay too.
Radioactivity
Radioactive decay is a spontaneous process that does not require an input of energy.
If the product of a nuclear reaction is unstable, it will decay too.
The process continues until unstable isotopes of one element are changed, into stable isotopes of a different element.
Stable isotopes are not radioactive.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

37. Nuclear Reactions Alpha emission Nucleons = PROTON OR NEUTRON
Note that mass number (A) goes down by 4 and atomic number (Z) goes down by 2.
Nucleons = PROTON OR NEUTRON
(particle in the nucleus)
Nucleons are rearranged but conserved

38. Nuclear Reactions Beta emission
Note that mass number (A) is unchanged and atomic number (Z) goes up by 1.
How does this happen?

39. Other Types of Nuclear Reactions
Positron (0+1b): a positive electron
207
K-capture: the capture of an electron from the first or K shell
An electron and proton combine to form a neutron.
0-1e + 11p --> 10n

40. Radioactive Decay Series

41. Writing Nuclear Reactions
Parent element = Reactant
Daughter element = Product
Radioactivity = radiation produced

42. Writing Nuclear Reactions
Law of Conservation of Mass
L. of C. of Charge
Isotopic Notation
Mass # and Nuclear Charge
146C = 147N + 0-1e

45. Key Concepts
Unlike chemical reactions, nuclear reactions are not affected by changes in temperature, pressure, or the presence of catalysts. Also, nuclear reactions of a given radioisotope cannot be slowed down, sped up, or stopped.
Three types of nuclear radiation are alpha radiation, beta radiation, and gamma radiation.
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.