Radiation: A Nuclear Change

Changes we know... Physical changes (solid, liquid, gas) –Matter changes energy and form, not composition Chemical changes (bonds, reaction) –Matter changes composition - atoms are rearranged to make new substances –Changes are based on movement of electrons (sharing, exchanging)

A New Kind of Change... Radiation –Change in the nucleus! –Emission of energy as electromagnetic waves or subatomic particles –Many types, we will discuss the three major ones: alpha, beta, gamma

Maria Goepprt-Mayer University at Göttingen (Germany) 1930, Theoretical Physics PhD (3 nobel prize winners in her doctoral board: Born, Franck, Windaus) Worked for free because no one would pay a woman scientist Explain “magic numbers”, stability of nuclear isotopes (1940’s) 1960 – paid professorship in U.S.A – Nobel Prize for physics b/c of magic numbers research

What atoms are radioactive? Radioisotopes –Some isotopes of an element have an unstable nucleus Why are some isotopes more stable? –Magic Numbers: –Arrangements of nucleons with higher than average binding rates

Nuclear stability chart

Nuclear Stability

What atoms are radioactive? Radioisotopes –Isotopes of an element that have an unstable nucleus What makes a nucleus unstable? –Relatively high amount of neutrons –Relatively small amount of neutrons –Atomic number greater than 83

Identify the radioisotopes! 1.Hydrogen Helium Calcium Neon Radium Radioactive! Too many neutrons Stable! Protons = neutrons Stable! P’s aprox = N’s Radioactive! Too many neutrons! Radioactive! Huge Nucleus

Can We Simplify these rules? An isotope is radioactive if... –It has too few or too many neutrons relative to the amount of protons –The nucleus is huge (atomic # greater than 83)

Now - the types of radiation

Alpha Radiation Alpha particle = 2 neutrons, 2 protons Q. After the alpha particle departs, what happens to the atomic number?

A.Atomic number changes by 2, B.So the element changes as well.

Beta Decay Neutron decays into both... –a proton (stays in nucleus) And –a Beta particle (electron that leaves)

Does the element change?

Gamma radiation Gamma radiation occurs to rid the nucleus of excess energy (often in conjunction with alpha or beta radiation) Energy Waves are emitted, not particles

Does the element change?

Relative masses... Alpha Beta Gamma

Stopped by... Alpha is stopped by paper Beta is stopped by Aluminum Gamma is stopped by lead *gamma can go through a Foot of concrete

When does the element change? Element changes when atomic # changes Atomic # indicates protons... Alpha radiation - emits 2p2n particle Beta - nucleus decays --> 1p & 1e(lost) Gamma - energy released, no particle change

More Comparison... How is mass affected? or atomic number?

Make this table... TypeEmittedStopped byEffect on mass Effect on atomic #

Make this table... TypeEmittedStopped byEffect on mass Effect on atomic # alpha2 n 2p paperDown 4Down 2 beta1n  p&e e-ejected aluminumnoneUp 1 Gamm a energyLeadNonenone