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Nuclear Decay
What forces are there in an atom?
Electronegative Force Positive/negative attraction
between protons and electrons. Relatively weak, but can be felt
for “long” distances Strong Nuclear Force
Not a positive/negative attraction.
Very strong, but only felt for short distances.
What did Einstein Think?
In the nucleus you have mass from the protons and neutrons and energy from the binding energy
The mass of a nucleus is less than the sum of all the protons and neutrons. This difference is called mass defect
Einstein said that the mass is lost because some of it can be converted to the binding energy.
E = mc2
E = binding Energy m = mass defectC = speed of light
Calculating Binding Energy
Find the mass defect and binding energy of an atom that has 2 neutrons and 1 proton. The actual mass of the nucleus is 3.016049. The mass of a proton is 1.007825 and the mass of a neutron is 1.008665.
Breaking a Nucleus Apart – Radioactive Decay
Radioactive Decay requires breaking parts of the nucleus or electrons off.
Three types of decay. Each breaks off a different piece of the atom Alpha releases a helium atom Beta releases an electron Gamma releases an antineutrino
Radioactive Decay
Happens Spontaneously A nucleus that undergoes radioactive
decay is said to be unstable. The atom can change identities
during radioactive decay. One atom becomes two separate
particles. Fission = splitting an atom into multiple
pieces.
Radioactive Decay - History
First Discovered by Henri Becquerel
Accidental Discovery Was working with Uranium and
noticed that it caused his photographic plates to have images.
Predicted that Images were due to released rays. ▪ Later discovered the rays were
Gamma Rays
Radioactive Decay - History
Marie Curie worked with radioactivity
Coined the term radioactivity and was the first to accurately describe all three types.
Pioneered treating cancer with radioactivity Ironically she died of cancer
due to all the exposure
Alpha Decay
Alpha Decay
Alpha particles make alpha rays Can be stopped by a piece of paper
Release the largest particles of all decay types
A Helium Atom symbolized by the Greek symbol α
α =He
42
Alpha Decay Uses
Used in Smoke Detectors Americium emits a steady stream of
alpha particles. Smoke disrupts that stream.
Pacemakers Alpha particles released at a specific
time interval. Will slow over time.
Alpha Decay Equation
Example equation for alpha decay
Sum of mass #= 210Sum of
atomic # = 84
Sum of mass # = 210Sum of
atomic # = 84
#1 RULE
For ALL types of decay, mass number and atomic number will be equal on both sides of the arrow. Matter cannot be created nor destroyed
– conservation of matter.
Beta Decay
Beta Decay
Beta particles make beta rays Can be stopped by an piece of aluminum
The middle in both size and danger. Electron is emitted and is given the
greek symbol β (beta).
β =e
0-1
Beta Decay Uses and Other Stuff
Too dangerous to have daily uses that we are exposed to.
Was discovered when Nitrogen appeared to violate the law of conservation of mass.
Sometimes called a neutrino.
Beta Decay Equation
Sum of Mass # = 8Sum of
Atomic # = 3
Sum of Mass # = 8Sum of
Atomic # = 3
Gamma Decay
Gamma Decay
Gamma Particles make Gamma Rays Can be stopped by very thick layers of lead or
other strong barriers. The smallest and the most dangerous Electron is emitted and is given the
Greek symbol γ (gamma).
γ =ν
00
Gamma Decay Uses and Other Stuff
Same gamma rays as the electromagnetic spectrum.
Uses Autoclaves kills bacteria and viruses Aimed at cancerous cells to treat them. Can change the color of gemstones
Was discovered by Marie Curie in Radium
Emitted particle sometimes called an antineutrino
Gamma Decay Equation
Sum of Mass # = 14Sum of
Atomic # = 6
Sum of Mass # = 14Sum of Atomic # = 6