Radioactive • Dennis Christian • Amirulhakim Hanif
Basic Concept • Inside an atom there are three kinds of particleprotonsneutronelectron • The nucleus contains protons and neutrons • The region beyond the nucleus contains electrons that balance out the charge of the protons • There are roughly as many protons as neutrons • Because like charges repel each other,there is always a force trying to push the protons apart • Provided there are not too many protons in the nucleus, other forces can hold the protons together • If the ratio of protons to neutrons is not within certain limits,protons may not be held firmly together,and they form an unstable nucleus.This is what makes isotopes of some elements radioactive.
Example • Carbon,the element found in all living things has the symbol C • The normal form (isotope) has an atomic weigh of 12 and is written as carbon-12, but the radioactive(isotope)version has two extra neutrons, so the symbol is carbon-14
Alpha Particle • The nucleus breaks down • A stable combination of two protons and two neutrons (alpha particle) is ejected from the nucleus as it decays • An alpha particle is also the nucleus of the atom of helium • If it captures two electrons, it becomes a natural helium atom • It does this by crashing into nearby atoms • All alpha particles readily transform into helium atoms
Beta Particle • The nucleus breaks down and eject an electron(beta particle) • What remains is a new element with a higher atomic number • This commonly happens in light elements • For example • Tritium(an isotope of hydrogen) breaks down into helium • Carbon changes to nitrogen • Nitrogen changes into oxygen
Gamma Radiation • The nucleus breaks and rearranges itself into a tighter cluster, sending out a wave of energy • The wave of energy is called gamma radiation • It is the same type of radiation as X-rays • Gamma rays caries enough energy to damage cells • This is how they kill living matter • It is for these reasons that radioactive sources should be shielded behind some absorbing material such as lead
Half Life • Half-life is the period of time taken for the amount of a substance undergoing decay to decrease by half • Half-lives are used to describe quantities undergoing exponential decay • Example, radioactive decay—where the half-life is constant over the whole life of the decay, and is a characteristic unit for the exponential decay equation. • A half-life can also be defined for non-exponential decay processes • Corresponding to sediments in environmental processes, if the half-life is greater than the residence time, then the radioactive nuclide will have enough time to significantly alter the concentration • A half-life describes the decay of discrete entities, such as radioactive atoms • It does not work to use the definition "half-life is the time required for exactly half of the entities to decay" • Example, if there is just one radioactive atom with a half-life of 1 second, there will not be "half of an atom" left after 1 second. There will be either zero atoms left or one atom left, depending on whether or not the atom happens to decay.
Half Life • An exponential decay process can be described by any of the following three equivalent formulas: • N0 is the initial quantity of the substance that will decay (this quantity may be measured in grams, moles, number of atoms, etc.), • N(t) is the quantity that still remains and has not yet decayed after a time t, • t1 / 2 is the half-life of the decaying quantity, • τ is a positive number called the mean lifetime of the decaying quantity, • λ is a positive number called the decay constant of the decaying quantity. • The three parameters t1 / 2, τ, and λ are all directly related in the following way: • where ln(2) is the natural logarithm of 2 (approximately 0.693)
Examples of Radioactive Elements Americium-241 432,7 Years Uranium-235 703,800,000 Years Specific Activity : 80,011 Bq/g atom% : 0.72% Weight % : 0.711% Activity % : 2,2% Activity in 1 g 2nat : 586 bq Uranium-238 4.468 · 109 years Specific Activity : 12,445 Bq/g atom% : 99.275% Weight % : 99.284% Activity % : 48.9% Activity in 1 g 2nat : 12,356 bq
Examples of Radioactive Elements Thorium Name of Element : Thorium Symbol of Element : Th Atomic Number of Thorium : 90Atomic Mass: 232.0381 amuMelting Point: 1750.0 °C - 2023.15 °KBoiling Point: 4790.0 °C - 5063.15 °KNumber of Protons/Electrons in Thorium : 90Number of Neutrons in Thorium : 142Crystal Structure: Cubic Density @ 293 K: 11.72 g/cm3 Color of Thorium : silvery Cesium-133 Isotope 133Cs Natural abundance : 100 Spin (I): 7/2 Frequency relative to 1H = 100(MHz): 13.116207 Receptivity, DP, relative to 1H = 1.00 : 0.0484 Receptivity, DC, relative to 13C = 1.00 : 276 Magnetogyric ratio, γ(107 rad T-1 s-1): 3.5332539 Magnetic moment, μ (μN) : 2.9277407 -3.43(10) and 302(21) [Mössbauer state] Line width factor, 1056l (m4) : 0.0000019 • Protactinium • Symbol: Pa • Atomic number: 91 • Atomic weight: 231.03588 (2) • Standard state: solid at 298 K • CAS Registry ID: 7440-13-3 • Group in periodic table: • Group name: Actinoid • Period in periodic table: 7 (actinoid) • Block in periodic table: f-block • Colour: silvery metallic • Classification: Metallic
Facts • One ton of natural uranium can produce more than 40 million kilowatt-hours of electricity. This is equivalent to burning 16,000 tons of coal or 80,000 barrels of oil. • One pound of uranium will make a ball only 1.3 inches in diameter. Make an "OK" sign with your forefinger and thumb to see how big that ball would be. • The price of uranium was approximately $10.75 per pound in early 2003. By mid 2006, the price had risen to approximately $45.00 per pound. In early 2007 the price approached $100.00 per pound. • Uranium boils at about 3,818 degrees Celsius • Development of Tiny Thorium Reactors Could Wean the World Off Oil In Just Five Years • One ton of thorium can produce as much energy as 200 tons of uranium and 3.5 million tons of coal • Thorium has huge potential for use as nuclear fuel in breeder reactors, especially since its chief isotope is "breedable" but is not useful for nuclear weapons.
Radioactive Effect on Human • Nausea • Vomiting • Headache • Some loss of white blood cell • Losing hair (with radiation exposure >200 rems) • Kill nerves cell at >5000 rems • Example: Hiroshima and Nagasaki Bombings • Chernobyl Accident
Rem is unit of effective absorbed dose of ionizing radiation in human tissue