Unit 17 Radioactivity

Atomic mass is the average number of p+ and n found in the nucleus. All elements have Isotopes. Atoms of the same element with a different number of neutrons found in the nucleus, therefore they have different masses. Carbon 12.0111 Chemical symbol: 1 or 2 letters used to represent an element. The 1st letter is always capital. If there is a 2nd letter, it is lower case. C 6 Atomic number is the number of p+ found in the nucleus.

Revolving around nucleus Subatomic Particles Particle Mass Charge Location in the atom Proton (p+) 1 amu 1.673 x 10-24 g +1 1.602 x 10-19 C Nucleus (center of atom) Neutron (n) 1.675 x 10-24 g Electron (e-) 1/1837 amu 9.109 x 10-28 g -1 -1.602 x 10-19 C Revolving around nucleus

Structure of the Atom Protons & Neutrons

Radioactivity All naturally occurring elements with atomic numbers greater than 83 are radioactive. Uranium is the largest naturally occurring element. Every element above 92 is man-made. Radioactivity is the uncontrollable decay of an atomic nucleus with the emission of particles and rays, with a lighter element formed. Radioactive elements can affect photographic plates, ionize gases, and cause physical effects (mutations).

half-life takes 4.5 billion years Po  Pb Half-life is the TIME it takes for ½ of the radioactive atoms to decay. Different elements take a different amount of time for a half-life to occur. U  Th half-life takes 4.5 billion years Po  Pb half-life takes 1.6 x 10-4 seconds

Radioactive Decay curve 1 line = 5 atoms Go from 0 to 120 atoms Radioactive Decay curve U  Th Po  Pb Atoms remaining 1 line = (depends of class data) Go from 0 rolls to ____ rolls Time (rolls)

For a single element, each half – life is the same amount of time. Remember that half-life is the period of time required for half of the atoms to go through decay. For a single element, each half – life is the same amount of time. So, if it takes 2 minutes for element X to go through one half – life, it takes 4 minutes to go through 2 half – lives. During each half – life, half of the atoms go through decay. remaining 1 g 1st half-life 2nd 3rd decayed ½ g ¼ g 1/8 g ½ g ¾ g 7/8 g

Radioactive Emissions Alpha particle a = Helium nucleus 4 He easily stopped Beta particle b = electron e- moderately difficult to stop Gamma ray g = pure energy very difficult to stop 2

How a Geiger Counter works Radioactive emission a or b causes ionization of Ar gas, completing circuit, clicks! How a Geiger Counter works

Radioactivity verses Distance Radioactivity (clicks/min) 1 line = 1 inch Go from 0 to 12 inches Distance (in) 1 line = depends on class data Go from 0 to ____

Effectiveness of Various Barriers to Radioactivity Card board Al Pb Radioactivity clicks/min 1 line = depends on class data Go from 0 to ? 1 line = 1 barrier Go from 0 to 10 barriers Number of barriers

Typical nuclear reactor

Drawing of the condition of Chernobyl reactor after the melt down

Chernobyl reactor after the melt down

Chernobyl reactor core

New structure that will enclose the destroyed reactor at Chernobyl. 500 feet long, 840 feet wide, and taller than the Statue of Liberty.

Fukushima Daiichi Power Plant Japan

Alpha decay a A X  A-4 N + 4 He Nuclear Notation A X Kinds of Decay Alpha decay a A X  A-4 N + 4 He N = new element Beta decay b A X  A N + e- N  p+ + e- Atomic mass Element symbol z Atomic number a Z Z-2 2 b Z Z+1

b a 241Pu 94 a b a a b

Calculating half-life of 137Ba 56 To calculate the half-life from data, determine the time when exactly half of the radioactive atoms remain. Radioactivity (clicks/min) Time (sec)

137 Ba  137 Ba Radioactive Decay of Ba to determine the half - life g 137 Ba  137 Ba Radioactive Decay of Ba to determine the half - life 56 56 Time (s) (clicks/min) 0 25,000 30 23,000 60 20,500 90 18,500 120 16,800 150 15,200 180 13,800 210 12,750 240 11,500 270 10,300 Time (s) (clicks/min) 300 9,400 330 8,700 360 7,800 390 7,000 420 6,200 450 5,600 480 5,050 510 4,650 540 4,200

Bikini island

http://en.wikipedia.org/wiki/File:Teller-Ulam_device.png

Review a a 1. a. 226Ra  222Rn  218Po 88 86 84 b b b. 214Bi  214Po  214At Top # = proton + neutron (atomic mass) 83 84 85 Bottom # = protons (atomic number) 2. Protons and neutrons are located in the nucleus, with the electrons located in energy levels around the nucleus. 3. Alpha a particle is a helium nucleus Beta b particle is an electron Gamma g ray is pure energy 4. 1/8 pound remaining 7/8 pound decayed 5. A device used to detect radiation by counting the number of emissions per unit of time

Nuclear chemistry Crossword Down 27. Cyclotron 28. Spectrograph 39. Meson Across 16. Emanations 18. Crystallization 34. Becquerel 40. Rutherford 45. Electroscope

Mushroom Cloud from a nuclear bomb. Size: 468 × 454 Type: 39KB JPG

Bikini Atoll is a circle of island with a deep central lagoon Bikini Atoll is a circle of island with a deep central lagoon.From 1946 to 1958 the US exploded 23 nuclear bombs to analyze what happens. All of the local people were relocated to another atoll before the explosions

Light Bright Assignment 1H 2H 3H . .. ... . . .