1. Radioactive Elements
Foundation Science 4 Class Code SC22102

2. Radioactivity
Radioactive decay – when the nucleus of an atom gives off energy or
particles.
Three types of decay:
1) Alpha (α) decay – gives off protons and neutrons
Particles
Nucleus of an atom

3. Radioactivity
Radioactive decay – when the nucleus of an atom gives off particles.
Three types of decay:
1) Alpha (α) decay – gives off protons and neutrons
2) Beta (β) decay – gives off an electron

4. Radioactivity
Radioactive decay – when the nucleus of an atom gives off particles.
Three types of decay:
1) Alpha (α) decay – gives off protons and neutrons
2) Beta (β) decay – gives off an electron
3) Gamma (γ) decay – gives off electromagnetic waves

5. So, Radiation can be energy
or a particle
Is bottom or top alpha decay? Beta decay? Gamma decay?
Gamma (γ) decay
Alpha (α) decay
Beta (β) decay

6. Differences
Thin material can stop most alpha (α) and beta (β) decay.
Gamma (γ) decay can only be stopped by thick metals such
as lead

7. Differences
Thin material can stop most alpha (α) and beta (β) decay.
Gamma (γ) decay can only be stopped by thick metals such
as lead

8. Radioactive Elements have
large atomic numbers
The more protons,
the more unstable
the atoms tend to be
Atomic
numbers
above 83 are
radioactive

9. Isotopes
Isotopes of an element have the same number of protons,
but different numbers of neutrons.
So, helium (He) has 2 protons . Isotopes of Helium all have
2 protons and 4 or 6 neutrons.
Some isotopes are unstable, and radioactive.

10. Isotopes

11. Symbols for Radioactivity
Radioactive Material Present

12. Geiger Counters
Geiger counters
measure radiation
When alpha, beta or
gamma radiation
hits the sensor, it
“clicks”

13. Geiger Counter
How stuff works
geiger video

14. Answer in Notebook
1. What are the three kinds of radioactive decay?
2. What kind of decay can only be stopped by a heavy metal like
lead (Pb)?
3. What kind of decay gives off electrons?
4. What is the only type of decay that gives off energy, and not
particles?
5. What is used to measure if the radiation level somewhere is safe
for humans?
6. In your own words, what is an isotope?
7. What kind of radiation is this??
8. Why do you think lead (Pb)
is so good at stopping
radiation?