Atomic Number & Mass Number • Atomic number = the number of protons • Mass number = the number of nucleons (protons & neutrons) • A neutral atom has the same number of protons and electrons.
Use your periodic table to find… The number of protons in a carbon atom The number of protons in a sodium atom The number of neutrons in a sodium atom The number of protons in a copper atom The number of neutrons in a copper atom The number of protons in a lead atom The number of neutrons in a lead atom The number of electrons in a lead atom
How many neutrons are there in a chlorine atom? Some chlorine atoms have 18 neutrons. Some have 19… They are “isotopes” of chlorine. (Chlorine–35 and Chlorine-36)
Three types of Nuclear Reactions Radioactive decay Fusion Fission
Alpha Radiation (α particle) • High-speed helium nucleus (+ve charge) • two protons & two neutrons • Can travel up to 10% of speed of light. • Range: a few centimetres • Can be stopped by a sheet of paper. • Can cause serious harm but cannot penetrate skin.
Beta Radiation (β particle) • High-energy electron (-ve charge) • Can travel up to 90% of speed of light. • Range: about 30 cm • Can be stopped by a sheet of aluminium about 5 mm thick.
Gamma Radiation (γRay) • Electromagnetic radiation with very high energy • Occurs as a result of a nucleus being left in a very excited state immediately following other types of radioactivity. • Travels at the speed of light. • Can penetrate through several centimetres of dense metal such as lead.