1. Aim # 45: What is Radioactivity?
H.W. # 45
Study pp
Ans. ques. p. 629 # 1,6-9
p. 630 # 11,12a,13,14a,15c

2. Element Protons NeutronsHe N O Ne S Cu Kr Bi U
Is there a trend in the relationship between the number of protons and the number of neutrons in an atom?
Given the stability of a nucleus, is there anything that seems peculiar about that?
Why does H have no neutrons?

3. I Radioactivity- the spontaneous breakdown of atomic nuclei accompanied by the release of sub-atomic particles and energy.
All isotopes of elements with atomic numbers greater than 83 (Bi) are radioactive (radioisotopes).

4. II Ernest Rutherford directed the radiation from various radioisotopes through an electric field.
What conclusion would you draw about radioactive emissions based upon the results?
There are 3 basic types.
Alpha particles- deflect toward the negative electrode.
Beta particles- deflect toward the positive electrode.
Gamma Rays- are not deflected.

5. Alpha (α) Helium nucleus 2+ 4 amu single sheet of paper Beta (β)
Type of Radiation
Composition
Charge
Mass
Able to be stopped by
Alpha
(α)
Helium
nucleus 2+
4 amu
single sheet of paper
Beta
(β)
electron 1-
1/1836
amu
thin sheet of aluminum
Gamma
(γ)
radiation
(energy)
several cm of lead

6. Identify X along with its mass number and atomic number. Ans. 234Th 90
III A. When an alpha particle is emitted as a result of nuclear disintegration, the reaction is called alpha decay.
e.g Ra → 222Rn + 4He
Problem: U → ?X + 4He ?
Identify X along with its mass number and atomic number.
Ans Th

7. B. When an atom emits a beta particle (beta decay),
When an atom emits an alpha particle, its at. no. decreases by 2 and its mass no. decreases by A NEW SUBSTANCE IS PRODUCED!
B. When an atom emits a beta particle (beta decay),
its at. no. increases by 1 and its mass number remains
the same.
Where do the new proton and electron come from?
Note: The electron (beta particle) comes from the nucleus!
1n → 1H + 0e
The difference between a beta particle and an electron is their source within the atom.

8. Problem: 234Pa → X + 0e 91 -1 Identify X , using the proper notation
Ans: 234U
Emissions of beta particles are often accompanied by the emission of gamma rays. .

9. IV Positron Decay- a positron has the mass of an electron, buy the charge of a proton. Positron decay occurs when a nucleus has too few neutrons relative to the number of protons
1p → 1n + 0e
β+ is another symbol for a positron.
at. no. decreases by 1, at. Mass remains the
same.
e.g B → 8Be + 0e
Problem: 15O → X + 0e
Ans: 15N

10. Identify each unknown X
230Th 90
222Rn 0e -1
4He 2
234U → X + 4He
X → 218Po + 4He
210Pb → 206Bi + X
210Po → 206Pb + X