The Atomic Nucleus https://www.youtube.com/watch?v=TJgc28csgV0

Review…the nucleus The nucleus is composed of particles called nucleons..__ & __ Neutrons and protons have the same mass, with ___ being slightly greater. Neutrons have nearly 2000 times the mass of _____. protons and neutrons neutrons electrons

Review…the atom The mass of an atom is almost equal to the mass of the _____ alone Nucleons are bound together by an attractive nuclear force called the ____ force The positively charged protons in the nucleus hold the negatively charged electrons in their ____ nucleus strong orbits

Review…the atom The principal role of the neutrons in the nucleus is to act as a sort of ____ to hold the nucleus together The electrical force acts as a ____ force between protons The atom needs a certain balance of neutrons and protons for ___ cement repulsive stability

The symbol was created in 1946 UC- Berkeley to represent “activity coming out of a atom”

What is Radioactivity? Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves. There are numerous types of radioactive decay. The general idea: An unstable nucleus releases energy to become more stable

Radioactive Decay

Radioactive Decay A neutron is very unstable. A lone neutron will spontaneously decay into a proton + an electron. If you have a lot of neutrons, within 11 minutes ½ of them will have decayed Particles that decay are said to be radioactive A lone neutron is radioactive

All the elements heavier than Bismuth (At # 83) are said to be radioactive

Their atoms emit 3 things…alpha, beta particles and gamma rays

Which is more penetrating?

Radiation Penetrating Power

Three Common Types of Radioactive Emissions - Penetrability Alpha particles may be completely stopped by a sheet of paper, beta particles by aluminum shielding. Gamma rays, however, can only be reduced by much more substantial obstacles, such as a very thick piece of lead.

Radiation Penetrating Power http://www.passmyexams.co.uk/GCSE/physics/penetrating-properties-of-radiation.html

Radioactive Isotope Iodine-131, a beta emitter, is taken as sodium iodide in drinking water. Almost all of it will find its way to the thyroid

Isotopes They are atoms of the same element that have different numbers of neutrons.

Radioactive Half-life

Radioactive Half-Life The half-life of an element is the time it takes for half of the material you started with to decay Remember, it doesn’t matter how much you start with. After 1 half-life, half of it will have decayed. Each element decays into a new element C14 decays into N14 while U238 decays into Pb206 (lead), etc The half-life of each element is constant. It’s like a clock keeping perfect time

Half-life

Half-life

Half-life

Half-life

“How much of this element remains after 4 half-lives? Just remember that at the end of one half-life, 50% of the element will remain. Find 50% on the vertical axis, Follow the blue line over to the red curve and drop straight down to find the answer:

Radiation Exposure to Americans

Used to measure radiation. Geiger Counter Used to measure radiation. The more intense the radiation the more “clicks”.

Review Name three of the science pioneers in the study of Radioactivity.? Why does a nucleus decay? Order these emissions from least to greatest penetrability: Gamma, Alpha, Beta. What is the greatest source of exposure to radioactivity in our everyday lives?