conventional x-ray tube the electron beam accelerates from a fila ment to an anode‚ where it decelerates rapidly at the anode and emits x-rays (shown schematically in Fig. 2). A different approach is to accelerate (or decelerate) the particle by passing it through a magnetic field. This is what really happens in an accelerator. When the particles curve in the magnetic field‚ x-rays are emitted. These x-rays are very collimated. The effective source is very small because the electrons can be focused down
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Metallic Bonding Metallic Bonding Why do metals conduct electricity? Metals conduct electricity. The delocalised electrons are free to move throughout the structure in 3-dimensions. They can cross grain boundaries. Even though the pattern may be disrupted at the boundary‚ as long as atoms are touching each other‚ the metallic bond is still present. Liquid metals also conduct electricity‚ showing that although the metal atoms may be free to move‚ the delocalisation remains in force until the
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of Radiation and Radioactivity Introduction: Radiation can be defined as the propagation of energy through matter or space. It can be in the form of electromagnetic waves or energetic particles. Ionizing radiation has the ability to knock an electron from an atom‚ i.e. to ionize. Examples of ionizing radiation include: • alpha particles • beta particles • neutrons • gamma rays • x-rays Non-ionizing radiation does not have enough energy to ionize atoms in the material it interacts with. Examples
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Rutherford was investigating physics everyday he tried lots of experiments. Rutherford showed that gamma rays were a type of X-ray‚ and that the alpha and beta rays were tiny particles of matter. Rutherford then showed that the beta particles were electrons. In 1908 Rutherford demonstrated and made an airtight glass tube with very thin walls‚ and filled it with the radioactive radium emanation. Alpha particles could penetrate the thin walls of the tube and were collected in a second tube. Rutherford
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example electron‚ proton and many more. Electric charge is the property responsible for electric forces which acts between nucleus and electron to bind the atom together. Charges are of two kinds (i) negative charge (ii) positive charge Electrons are negatively charged particles and protons‚ of which nucleus is made of‚ are positively charged particles. Actually nucleus is made of protons and neutrons but neutrons are uncharged particles. electric force between two electrons is same
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Reduction/Oxidation Reactions • Oxidation number: The charge that an atom in a molecule would develop if the most electronegative atoms in the molecule took the shared electrons from the less electronegative atoms. • Oxidation numbers are not real; they are only based on assumptions. They are useful bookkeeping tools though‚ and can help us keep track of electrons during a reaction. • The sum of all oxidation numbers in a molecule must equal the charge of that molecule. • Rules 1-4 about oxidation numbers: what’s
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3 Name: Flame Tests & Electron Configuration Pre-Laboratory Questions and Exercises Due before lab begins. Answer in the space provided. 1. Write electron configuration for the alkali metals Li‚ Na‚ K‚ and Rb. Li ____He 2s1_____________________________________________ Na ____Ne 3s1______________________________________________ K _______Ar 4s1___________________________________________ Rb _______Kr 5s1___________________________________________ 2. Write the electron configuration for strontium
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particles that form together to create an atom of an element; protons‚ neutrons‚ and electrons. Protons are positively charged and form the nucleus of an atom with neutrons that carry no charge. Electrons are negatively charged and are constantly moving around the nucleus. Ions are created when electrons move from one atom to another atom changing the charge of that atom to either positive or negative. When electrons move they form bonds. There are two types of bonds; ionic and covalent. Ionic bonds
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electrostatic force between two charges of 200 µC and 500 µC placed in free space is 5 gf. Find the distance between the two charges. (g = 10 m/s2) 12. Derive an expression for the electric current in terms of drift velocity. How the drift velocity of the electron depends on the temperature of
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to say that H2O has a “covalent bond”‚ let’s look at the definition of a covalent bond: A covalent bond is a chemical bond that involves the sharing of electron pairs between atoms. The stable balance of attractive and repulsive forces between atoms when they share electrons is known as covalent bonding. For many molecules‚ the sharing of electrons allows each atom to attain the equivalent of a full outer shell‚ corresponding to a stable electronic configuration. (Source: http://en.wikipedia.org/wiki/Covalent_bond)
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