9/22/2011 Basic Chemistry Why are we studying chemistry? • Biology has chemistry at its foundation Elements • All matter composed of basic substances called elements • Living organisms require about twenty of the known elements Together‚ carbon‚ hydrogen‚ nitrogen and oxygen make up 95% of the elements found in the body. Atoms • All elements made of tiny particles called atoms • Made up of: – Nucleus • contains protons (+ charge) and neutrons (no charge) – Outside
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Xxx.comTheories of light In the seventeenth century two rival theories of the nature of light were proposed‚ the wave theory and the corpuscular theory. The Dutch astronomer Huygens (1629-1695) proposed a wave theory of light. He believed that light was a longitudinal wave‚ and that this wave was propagated through a material called the ’aether’. Since light can pass through a vacuum and travels very fast Huygens had to propose some rather strange properties for the aether: for example; it must
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Chemical bond From Wikipedia‚ the free encyclopedia A chemical bond is an attraction between atoms that allows the formation of chemical substances that contain two or more atoms. The bond is caused by the electrostatic force of attraction between opposite charges‚ either between electrons and nuclei‚ or as the result of a dipole attraction. The strength of chemical bonds varies considerably; there are "strong bonds" such ascovalent or ionic bonds and "weak bonds" such as dipole–dipole interactions
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structures‚ to predict the shape of those molecules‚ and whether or not the molecules are polar. Introduction: A. Covalent Bonds and Lewis Structures When elements combine‚ there are two types of bonds that may form between them: Ionic bonds result from a transfer of electrons from one species (usually a metal) to another (usually a nonmetal or polyatomic ion). Covalent bonds result from a sharing of electrons by two or more atoms (usually nonmetals). Lewis theory (Gilbert Newton Lewis
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potential energy). The positive end of a polar molecule will attract the negative end of the other molecule and influence their arrangement. Dipole-dipole forces have strengths that range from 5 kJ to 20 kJ per mole. They are much weaker than ionic or covalent bonds and have a significant effect only when the molecules involved are close together (touching or almost touching). London Dispersion London dispersion forces are a type of force acting between atoms and molecules. It is caused by correlated movements
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electrons in an atom or ion determines the number and kinds of chemical bonds that can be formed Ch 3.3 first page How Atoms Bond http://www.youtube.com/watch?v=QqjcCvzWwww&list=PL3FE5B87E56E7A849&index=3 9 List the three types of chemical bonds and explain the circumstances under which each forms. Ch 3.3 “Ion Formation” “Covalent Bonding” “Polarity in Water Molecules and Hydrogen Bonding” How Atoms Bond; Examples of Hydrogen Bonds http://www.youtube.com/watch?v=QqjcCvzWwww&list=PL3FE5B87E56E7A849&index=3
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Core Module 1: The Chemical Earth Contextual Outline The Earth includes a clearly identifiable biosphere‚ lithosphere‚ hydrosphere and atmosphere. All of these are mixtures of thousands of substances and the use of this pool of resources requires the separation of useful substances. The processes of separation will be determined by the physical and chemical properties of the substances. In order to use the Earth’s resources effectively and efficiently‚ it is necessary to understand the properties
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be used to infer the number of valence electrons in an atom? (Chapter 7 ) (106) Draw electron dot structures and predict the shapes of the following molecules. (Chapter 8) a. PH3 b. CO c. CS2 d. CF4 (107) How are single‚ double‚ and triple bonds indicated in electron dot structures? (Chapter 8) (108) Give an example
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1.1 The atoms‚ during bond formation‚ may lose or gain electrons (valence electrons) in order to achieve a stable state‚ or technically speaking‚ a stable electron configuration. Usually metal atoms lose electrons and non-metals gain electrons in order to achieve electron stability. When dealing with bond formation (Ionic bonding for example) we need to analyse the outer shell of the atom. Metals usually present 1‚ 2 or 3 electrons in their outer shell therefore they have to give them away to achieve
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Hwa Chong Institution (High School) Secondary 4 End of Year Examinations Chemistry Revision Notes List of topics: 1. Atomic Structure 2. Separation Techniques 3. Chemical Bonds and Bonding (Ionic‚ Covalent) 4. Metals 5. Properties and structures of compounds 6. Qualitative Analysis 7. Acids‚ Bases and Salts 8. Chemical Periodicity 9. Chemical Calculations 10. Air and Environment 11. Electrochemistry (Including Redox reactions) 12. Thermochemistry 13. Rates of Reaction 14. Chemical
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