Integrated Science - Chapter 25 Notes
I. What is Radioactivity?
- Process by which an unstable __________ emits one or more particles or __________
 Nucleus is composed of __________ and __________
 __________ are __________ the nucleus
A. Nuclear decay
- Break down of an __________ nucleus
- Element can become an __________or a new __________
- Isotopes – atoms of the same element with different numbers of __________
- Some isotopes are __________ and never break down, while some are unstable
and __________ down into a more stable atom.
- Some reasons that an isotope of an element might be __________ are:
 Too many __________ in the nucleus
- Carbon-12 (6 protons, 6 neutrons) is stable, but Carbon-14
(6 protons, 8 neutrons) is unstable.
 Too __________ neutrons in the nucleus
- Beryllium-7 (5 protons, 2 neutrons) is unstable, but Beryllium-9
(5 protons, 4 neutrons) is stable.
 Nucleus is too big in __________ (too many neutrons and protons total)
- All elements atomic __________ and higher are unstable due to
their large nucleus size.
B. When a nucleus decays, it breaks down into a new __________, plus ejected nuclear __________
 This is a __________ occurring / spontaneous event when a nucleus is unstable
C. There is a “__________ Nuclear Force” present in the nucleus of an atom which holds the
__________ and __________ together in the nucleus to remain stable.
 Kind of like nuclear “__________”
D. Types of Nuclear Radiation
- Nuclear radiation – __________ or uncharged particles or energy emitted by unstable nuclei
- All radiation can __________ with and affect surrounding __________
- _______________ – change from one element into a new element plus nuclear radiation
- 4 Types of nuclear radiation
1. __________ particles (α) – positively charged, made of ___ protons and ___ neutrons
- Most __________ nuclear radiation particle
- __________ moving, and quickly loses __________
2. __________ particles (β) – __________ charged, made of fast moving __________
- __________ mass
- Penetrate matter, but not __________
3. __________ rays (γ) – high __________, high penetrating power
- __________ made of matter, no charge
- Electromagnetic energy like light or x-rays, but with more energy
- Stopped by 7 cm of lead
- __________ hazard due to energy and penetrating ability
4. __________ emission – a single __________ with no charge
- Can penetrate up to ______ cm of lead
II. Nuclear Reactions
A. Much __________ released into the surroundings during a nuclear reaction
B. In a nuclear reaction, the nucleus __________
 There are __________ types of nuclear reactions:
1. Nuclear ________ – process where a nucleus __________ (or is split) into two or more smaller
nuclei and __________ energy
 Particles can cause __________ reactions of nuclear fission in surrounding atoms
- This is an example of a nuclear __________
- Some practical uses of fission reactions are:
 Nuclear reactors for a __________ source
 __________
 __________
2. Nuclear Fusion – process where two nuclei __________ at very high temperatures to
form a larger nucleus and releases energy
 This occurs continuously in __________ as hydrogen atoms (1 proton, 1 neutron) are
joined together to form __________ atoms (2 protons, 2 neutrons).
 During the process, a __________ amount of __________ is also __________.
- Some practical uses of fusion reactions are:
 We use this energy (__________ energy) to warm the __________, and __________
 Plants use it to make food (_______________).
 We can __________ and convert solar energy into __________.
C. Nuclear reactions, mass, and energy
 In both fission and fusion reactions, a small amount of __________ is converted into a large
amount of __________ during the reaction.
 The Law of Conservation of __________ still applies, as matter (which has mass) is not
created or __________, but the form is __________.
 During the change in form, energy is __________ as the matter becomes more stable, with
__________ energy.
III. Dangers and Benefits of Nuclear Radiation
- There are both __________ and negatives to __________ radiation and nuclear __________
A. Dangers  can __________ skin, can ionize living __________, can destroy cells, can cause
__________, can cause genetic __________ in DNA, radiation __________
B. Benefits  can be used to __________ diseases, used in __________ detectors, tracers used in
__________, __________, research, __________ source
C. There are __________sources of radiation all around you.
 __________ gas in the atmosphere and soil
 Carbon-14 inside your __________ and every living thing
 __________ (medical, from the sun, from elements in the earth)
 Cosmic __________ from space
 Rocks and __________ with radioactive materials
IV. Half-life
- Some radioisotopes decay to stable atoms in less than a ____________.
- However, the nuclei of certain radioactive isotopes require millions of ____________ to decay.
- A measure of the ____________ required by the nuclei of an isotope to decay is called the ______-life.
- The half-life of a radioactive isotope is the amount of time it takes for half the nuclei in a sample of the
isotope to decay.
- The nucleus left after the isotope decays is called the ____________ nucleus.
- Half-lives ____________ widely among the radioactive isotopes.
- The number of half-lives is the amount of ________ that has passed since the isotope began to decay.
- For example:
If you have 100 atoms of a sample of Carbon-14, and the half-life of that isotope is 5730 years,
how many atoms are left after 2 half-lives?
100 atoms  50 atoms  25 atoms
1st half-life
2nd half-life
2nd Example :
If you started with 1000 atoms of a sample of Iodine-131, and you have 8 atoms left, how much
time has passed?
Half-life of Iodine-131 = 8.04 days
Step 1: Determine number of half-lives
1000 500 250 125 63 32 16 8
1
2
3
4
5
6
7
**7 half-lives**
Step 2: What is the half-life of the isotope?
 Half-life of Iodine-131 = ____________days
Step 3:
Multiply # of half-lives and half-life time
______ half-lives x 8.04 days = ___________ days
half-life