1. Aim # 47: How can we obtain energy from the nucleus of an atom?
H.W. # 47
Study pp (sec. 19.2)
pp (sec )
Ans. ques. p. 630 # 16-19
Complete handout sheet

2. Do Now:
60Co → X + 0e
Identify X
If you had a 20.g sample of 60Co, how much of the isotope would remain after years?

3. 60Ni 28
t = y
From Ref. Table N, T = 5.26 y
fraction remaining = (1/2)15.78/5.26 = (1/2)3
= 1/8
mass remaining = 20.g/8 = 2.5g

4. I Transmutation- when one element is changed into another element as a result of a change in the nucleus (decay).
II Artificial Transmutation- the nucleus of an element is bombarded with high energy particles such as protons, neutrons, or alpha particles to produce a radioactive isotope of a new element.
e.g. 4He N → 1H + 17O
alpha particle nitrogen proton oxygen

5. The same must be true for the atomic numbers.
Problem: What nucleus (element) is represented by X in the following transmutation?
X + 1H → 6Li + 4He
Note: the sum of the mass numbers on each side of the equation must be equal.
The same must be true for the atomic numbers.
Problem: 14N + 1n → X + 1p Identify X

6. How do we calculate the atomic mass of an atom?
For an atom of helium,
mass of protons = ( x 10-24g) x 2 = x 10-24g
mass of neutrons = ( x 10-24g) x 2 = x 10-24g
Total = x 10-24g
HOWEVER, the mass of the nucleus is found experimentally to be x 10-24g!
There is a deficiency of x 10-24g in every atom of He.

7. The energy is called the nuclear binding energy of the atom.
III Mass Defect- the difference in mass between the mass of a nucleus and the sum of the masses of its individual protons and neutrons.
The difference has been converted to energy according to Einstein’s equation
E = mc2
The energy is called the nuclear binding energy of the atom.
As binding energy ↑, stability of the atom ↑.

8. IV Nuclear Fission- the “splitting” of heavier nuclei into two lighter ones.
91Kr (or 3)
fast moving neutrons
Slow moving neutron U
142Ba

9. 1. A radioactive nucleus captures a slow moving neutron, becoming unstable.
2. The unstable nucleus splits to form two lighter
fission fragments.
3. Energy (γ radiation), β particles, and 2 or 3
high-speed neutrons are also released.
4. Only unstable elements of high atomic number
may be fissioned.
Note: Each splitting of an atom produces different pairs of smaller atoms.

10. B. Fission Chain Reaction
+ energy! etc.
Uncontrolled, such a chain reaction for 235U, for example, can release 80,000 kJ for every 1g that reacts-
much more energy than ordinary chemical reactions.