Unit 2: The Atom Nuclear Decay

Band Of Stability  Atoms that lie outside the band of stability are unstable  Atoms 1-20 n 0 /p + ratio must be 1:1  Atoms n 0 /p + ratio is ~ 1.5 : 1  Atoms 84 and up are ALL unstable  Unstable atoms will lose pieces of itself until it becomes stable. – This is Nuclear Decay

3 Types of Decay Region A: Atoms have too many neutrons; Beta Decay Region B: Atoms have too many protons; Positron emission and e - capture Region C: Elements have too many neutrons and protons; Alpha Decay

Alpha Decay  I am an isotope that have too many neutrons and protons… What to do?  Alpha decay!!!  Atoms that undergo alpha decay lose 2 protons and 2 neutrons  α (alpha particles)are simply the nucleus of a He atom with no electrons!!)  The result is an atom with lower atomic number and mass

Alpha Decay Alpha decay is how elements greater than atomic #83 try to become stable. They will emit an alpha particle (2 neutrons and 2 protons) to try to become stable. Alpha reactions will always have He on the right side! To balance: write the upper and lower equations! 210= =82 + 2

Beta Decay  I am an isotope with too many neutrons… what to do?  Get rid of a neutron by Beta Decay!  During Beta decay, a neutron is converted into a proton and e - (which is ejected from the nucleus) Neutron = proton + electron  Beta particles are known as high energy electrons  The extra proton creates an atom with a higher atomic number There are 2 ways to write a Beta particle!

Beta Decay Beta decay is how elements who have too many neutrons try to become stable (on top of the band) Beta reactions will always have ß or e- on the right side! 14 = =

Gamma Decay  Gamma decay never happens alone! (it usually accompanies alpha or beta decay)  It represents a photon of energy or light  Gamma decay alone involves no transformation or change of an atom’s nucleus

Gamma Decay The * represents extra energy that will be lost. 93 = =

Practice For each of the following, fill in the missing parts of the equation: 131 Rn

Nuclear Decay Series Radioactive atoms will continue to decay until they reach a stable nucleus. For large atoms with atomic number greater than 83, the stable element will be lead.

Nuclear Decay Series

Detecting Radiation  Radioactive particles can be detected by a Geiger Counter which gives a clicking sound for each particle detected.  Different types of radiation required different types of protection.  The greater the distance from a radioactive source will give better protection.

Radiation Safety Alpha Particles  Cannot penetrate very far into matter.  Cannot penetrate a sheet of paper.  Cannot penetrate your skin.  Only dangerous to humans if eaten or inhaled.

Beta Particles  Can penetrate a bit more deeply  Can be stopped by a sheet of aluminum foil or plexiglass.  Only dangerous to people if eaten or inhaled.

Gamma Particles  The most penetrating (have the most energy).  They will penetrate the body through the skin and do damage.  Have more energy than an x-ray  Can only be stopped by thick pieces of lead

Radiation Safety