1. 3-4 Changes in the Nucleus

2. Nuclear Reactions Changes do occur in the nucleus.
Called a nuclear reaction
Changes the composition of an atoms nucleus
Alpha and beta radiation comes from the nucleus.

3. Nuclear Stability Very few atoms are radioactive
The question is WHY are some unstable.
Has to do with number of protons and neutrons
Not all combinations are stable

4. You would think positively charged protons would repel each other in a nucleus.
An attractive force holds together the protons and overcomes the electric force
Called STRONG NUCLEAR FORCE
Only significant with subatomic particles
See Figure 3-27 pg. 112 in book

5. Neutrons, which experience no electric charge, do experience the strong nuclear force
The presence of neutrons seems to hold together the nucleus.

7. Composition of Stable Nuclei
As the number of protons increases, it takes more and more neutrons to remain stable.
All atoms above 83 are unstable

8. Types of Radioactive Decay
Alpha Radiation- Stream of high energy alpha particles.
Consists of 2 protons and 2 neutrons
Identical to a helium-4 nucleus
Symbol 42He2+ or 42He or 42
Do not cause a health risk
Do not travel far

9. . Beta Radiation- a stream of high speed electrons
A neutron changes into a proton and electron
The proton stays in the nucleus
The electron is propelled out at high speed
Symbol of 0-1e- or 0-1e or 0-1
Note – the 0 should be above the –1
Is damaging to skin

10. Gamma radiation –
Extremely energetic form of light energy we can not see
Symbolized by 00
Does not consist of particles
Able to penetrate deeply into substances

11. Types of Radiation Name Identity Charge Pen. Ability Alpha ()
Helium-4 nuclei 2+
Low
Beta ()
Electron 1-
Medium
Gamma ()
High energy particle
None
high

12. When an atom emits one of these, it is said to be undergoing radioactive decay
Which brings us to the nuclear equation, or a way to keep track of the components

13. Alpha Decay

15. Beta Decay

17. In any radioactive decay, the sums of the mass numbers and the atomic numbers are the same before and after the reaction

18. Practice Problems
Write the nuclear equation for the alpha decay of uranium 238.
Write a nuclear equation for the beta decay of sodium 24

19. Other Nuclear Reactions
Nuclear Fusion
Atoms collide and join together releasing great amounts of energy
Like in the Sun
Nuclear Fission
Splitting the nuclei of large atoms
Like in Nuclear reactors