Medical Chemistry Lecture 6 - Radiochemistry PDF

Al Rashed university College Department of Dentistry 1st stage Medical chemistry Lecture 6 Radiochemistry  Radiochemistry | Ali Hazim Radiochemistry...

Al Rashed university College Department of Dentistry 1st stage Medical chemistry Lecture 6 Radiochemistry  Radiochemistry | Ali Hazim Radiochemistry Radiation is invisible energy waves or particles. The radioactivity is the property of some atoms to spontaneously give off energy as particles or rays. the atoms that make up the radioactive materials are the source of radiation. 1- Isotopes: are atoms of a particular chemical element, which have differing numbers of neutrons 2- Radioactivity: it is the emission of particles and energy by isotope 3- Radioactive decay: it is an atomic nucleus of an unstable atom loses energy by emitting ionizing particles (ionizing radiation) 4- Nuclear radiation: the nuclei of unstable isotopes undergo spontaneous nuclear reaction that causes liberation of new particles and energy. The radiation three types, called alpha, beta or gamma radiation 1) α (alpha) radiation:- it is contains 2 protons and 2 neutrons from an atomic nucleus When this occurs, the atom s atomic mass will decrease by 4 units and atomic number will decrease by 2 particles. Properties of Alpha Particles 1- 2 neutrons and 2 protons 2- Charge of +2 3- Emitted from nucleus of radioactive atoms 4- Transfer energy in very short distances 10 cm in air) 5- Shielded by paper or layer of skin 6- causing local damage in tissue (kidney, liver, lung, spleen). 1  Radiochemistry | Ali Hazim Alpha Radiation α has the same constitution as a helium nucleus Alpha particle may be written as. They have a double positive charge and a mass of 4 unit. 𝟒𝑯𝒆 𝒐𝒓 𝟒𝑎 𝟐 𝟐 2) β (Beta) radiation:- the transmutation of a neutron into an electron and a proton. After this happens, the electron is emitted from the nucleus into the electron cloud. Properties of Beta particles 1- Small electrically charged particles 2- Similar to electrons 3- Charge of -1 4- Ejected from nuclei of radioactive atoms 5- Shielded by wood, body penetration 0.2 to 1.3 cm depending on energy 6- Can cause skin burns Beta Radiation β- is produced when a neutron decays Beta minus particles may be written as They have a negative charge and a mass of 1/1800 unit. 𝟎 − 𝟎 − −𝟏 𝖰 𝒐𝒓 −𝟏 𝒆 β- is produced when a neutron decay 𝟏𝒏 → 𝟎𝖰 − + 𝟏 𝒑 𝟎 −𝟏 𝟏 3) ɣ (Gama) radiation:- it consists of photons with a frequency of greater than 1019 Hz. It is much like X-rays, and can pass completely through the human body. Thus, gamma rays emitted from outside of the body may cause ionization, and possible health effects, in any organ in the body. Properties of Gama radiation 1- Electromagnetic photons or radiation (like x-rays) 2- Emitted from nucleus of radioactive atoms spontaneous emission 3- Highly penetrating- extensive shielding required 4- radiation hazard 2  Radiochemistry | Ali Hazim Gamma Radiation Gamma rays are a form of electro-magnetic radiation ɣ release is often associated with α or β decay Gamma rays remove energy from an unstable nucleus. Positron: the same electron mass but opposite charge (+) Because positron is considered to β+ some references used negatron for β- and positron for β+ B+ particles are positrons 𝟏𝒑 → 𝟏𝒏 + 𝟎𝖰 + 𝟏 𝟎 +𝟏 X- rays: have smaller wavelengths and energy higher than ultraviolet waves X-ray light tends to act more like a particle than a wave X-rays have a wavelength in the range of (0.01 to 10 nm), and energies in the range 120 ev to 120 kev. X-ray can form ions in matter by knocking electrons off the atoms and molecules in its path creating ions, that’s why it is called ionization radiation. Properties of X-rays 1- Overlap with gamma rays 2- Electromagnetic photons or radiation 3- Produced from free electrons 4- Emitted with various energies and wavelengths 5- Highly penetrating- extensive shielding required 3  Radiochemistry | Ali Hazim 6- External radiation hazard Penetrating power α has a high mass, it is stopped by a few centimeters of air β has a small mass, it is stopped by a few millimeters of aluminum Ɣ has zero mass, It is stopped by thick lead or concrete. Ionization radiation Ionizing radiation is produced by unstable atoms, because they have an excess of energy or mass or both. Ionizing and non-ionizing radiation 1- Radiation carries a range of energy forming an electromagnetic spectrum 2- Radiation that does not have enough energy to break chemical bonds is referred to as Non-ionizing Radiations, radio waves, microwaves, infrared, visible light. 3- Radiation that has enough energy to break chemical bonds is referred to as ionizing radiation, alpha particles, beta particles, gamma rays 4  Radiochemistry | Ali Hazim Nuclear reactions Some radioisotopes contain nuclei which are highly unstable and decay spontaneously by splitting into two smaller nuclei Such spontaneous decays are accompanied by the release of neutrons. Nuclear reaction can be induced by bombarding atoms with neutrons. The nuclei of the atoms then split into two parts Induced fission decays are also accompanied by the release of neutrons. In nuclear reaction, two nuclei with low mass numbers combine to produce a single nucleus with a higher mass number. Half life 1- It is the time needed for one half of the original nuclei of an isotope to decay to other substances (t1/2) 2- The importance of half-life, it tells us how long a sample of isotope will exist. ionization radiation has been known to cause 1- Skin cancer. 2- Bone cancer. 3- Leukemia. 4- Other types of cancer. 5- Damage to brain cells. 6- Eye cells. 7- Damage to other cells and tissues. 8- Genetic risk, this type of risk causes damage to genes of the cell nuclei). The Effects of Radiation on the Cell at the Molecular Level 1- When radiation reactions with target atoms, resulting in ionization 2- The absorption of energy produces damage to molecules 3- damage occurs to atoms in the biologic system. 4- The production of free radicals whose toxic damage in a biologic effect 5