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