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 largenucleus 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-life2nd 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