U-235Symbol of ElementMass numbeHow do you know the atomic number?Find U in the periodic table. Symbols for IsotopesZ = 92
How are isotopes of the same element alike and different? Alike: 1. Number of protons and electrons 2. Atomic number 3. Chemical properties Different: 1. Number of neutrons 2. Mass Number 3. Atomic mass of the isotopes
Types of Radiation • Isotopes of atoms with unstable nuclei are called radioisotopes . • Unstable nuclei emit radiation (release energy) to attain more stable atomic configurations in a process called radioactive decay . • The three most common types of radiation are alpha , beta , and gamma . SECTION 2 4.1 Nuclear Radiation Isotope - Atoms of the same element with different number of neutrons .
Types of Radiation (cont.) SECTION 2 4.1 Nuclear Radiation
He 4 2 A. Types of Radiation • Alpha particle ( ) – helium nucleus paper 2+ Beta particle ( -) electron e 0 -1 1- lead Positron ( +) positron e 0 1 1+ Gamma ( ) high-energy photon 0 concrete
• Alpha particles have the same composition as a helium nucleus — two protons and two neutrons. • Because of the protons, alpha particles have a 2+ charge. • Alpha radiation consists of a stream of particles. SECTION 2 4.1 Nuclear Radiation Types of Radiation (cont.)
• Alpha radiation is not very penetrating — a single sheet of paper will stop an alpha particle. SECTION 2 4.1 Nuclear Radiation Types of Radiation (cont.)
• Beta particles are very fast-moving electrons emitted when a neutron is converted to a proton. • Beta particles have insignificant mass and a 1 – charge. SECTION 2 4.1 Nuclear Radiation Types of Radiation (cont.)
• Beta radiation is a stream of fast moving particles with greater penetrating power — a thin sheet of foil will stop them. SECTION 2 4.1 Nuclear Radiation Types of Radiation (cont.)
• Gamma rays are high-energy electromagnetic radiation. • Gamma rays have no mass or charge. • Gamma rays almost always accompany alpha and beta radiation. • X rays are a form of high-energy electromagnetic radiation emitted from certain materials in an excited state. (gamma rays) SECTION 2 4.1 Nuclear Radiation Types of Radiation (cont.)
• The ability of radiation to pass through matter is called its penetrating power . • Gamma rays are highly penetrating because they have no charge and no mass. SECTION 2 4.1 Nuclear Radiation Types of Radiation (cont.)
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