Radioactivity Chapter 19

Forces inside an atom 1) Electromagnetic force: a) attracts electrons(-) to protons(+) b) protons repel each other (+,+) c) long range 2) Strong force: attraction of nucleons for each other (protons & neutrons = nucleons) strongest force in the universe but.. very short range

Nuclear Force interactions 1) All nucleons attract each other 2) Only protons repel each other 3) More neutrons = more attraction with out adding any repulsion (Neutrons called nuclear cement)

Nuclear Force interactions 4) more neutrons add stability to atoms unless…… too many neutrons w/o protons nearby neutrons that are by themselves decay the neutron spits out an electron and turns into a proton the electron that shoots out is a beta particle (beta radiation)

Nuclear Force interactions H-3 (tritium) decays to Helium

Nuclear Force interactions Neutron mass is greater than proton mass by slightly more than 1 electron (1/1800 amu) Extra mass is converted to energy Ve

Law of conservation of Matter??!! The extra matter is not destroyed…… it is converted into energy E = mc2 E is the energy produced m is the amount of mass converted C is the speed of light

Beta radiation 1) produced by beta decay 2) = a very fast moving electron 3) can penetrate human skin 4) damages DNA = mutations & cancer a) most dangerous to growing cells b) babies & children c) cancer cells ….so beta radiation used to treat cancer

Alpha radiation -origin 1) Happens when too few neutrons 2) Nucleus unstable bcs strong force can’t reach across large nuclei but Electromagnetic force can!

Alpha radiation- origin 3) pieces of large unstable nucleus break off 4) the pieces are alpha particles 5) alpha particles consist of 2 protons & 2 neutrons

Alpha radiation-effects Atom changes to different element Atomic number decreases by 2 Atomic mass decreases by 4 amu

Alpha radiation -characteristics 1) largest radiation particle & + charge so can’t penetrate through skin 2) can damage internal tissues if inhaled or swallowed 3) can cause cancer… radon gas 4) alpha particles pick up electrons to become helium w/i a few cm

Gamma radiation Pure energy ….has no mass Very high energy light wave (not visible) Generated by the sun Can penetrate most materials Can harm & kill cells Can cause cancer, birth defects & shortened life span