 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.

 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 = mc 2 E = binding Energy m = mass defect C = speed of light

Find the mass defect and binding energy of an atom that has 2 neutrons and 1 proton. The actual mass of the nucleus is The mass of a proton is and the mass of a neutron is

 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

 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.

 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

 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 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 4 2

 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.

 Example equation for alpha decay Sum of mass #= 210 Sum of atomic # = 84 Sum of mass # = 210 Sum of atomic # = 84

 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 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

 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.

Sum of Mass # = 8 Sum of Atomic # = 3 Sum of Mass # = 8 Sum of Atomic # = 3

 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 0 0

 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

Sum of Mass # = 14 Sum of Atomic # = 6 Sum of Mass # = 14 Sum of Atomic # = 6