1. CHAPTER 24 Nuclear Energy
I. Radioactivity
(p ) 1 1

2. A. Definitions Radioactivity
emission of high-energy radiation from the nucleus of an atom
Nuclide
nucleus of an isotope
Transmutation
process of changing one element into another via nuclear decay

3. B. Types of Radiation 2+ 1- Alpha () helium nucleus Beta-minus (-)
paper 2+
Beta-minus (-)
electron
lead 1-
Gamma ()
high-energy photon
concrete

4. C. Nuclear Decay Why nuclides decay…
to obtain a stable ratio of neutrons to protons
Stable
Unstable
(radioactive)

5. C. Nuclear Decay
TRANSMUTATION
Alpha Emission
Beta Emission

6. D. Half-life Half-life (t½)
time it takes for half of the nuclides in a sample to decay
Example Half-lives
polonium seconds
lead hours
iodine days
carbon-14 5,370 years
uranium billion years

7. D. Half-life total time = 30 hours number of half-lives = 2
How much of a 20-g sample of sodium-24 would remain after decaying for 30 hours? Sodium-24 has a half-life of 15 hours.
GIVEN:
total time = 30 hours
t1/2 = 15 hours
original mass = 20 g
WORK:
number of half-lives = 2
20 g ÷ 2 = 10 g (1 half-life)
10 g ÷ 2 = 5 g (2 half-lives)
5 g of 24Na would remain.