4.1 Defining the Atom Overview cannot be seen w/ naked eye def. smallest particle of an element that retains its identity in a chemical reaction Democritus’ Atomic Philosophy Democritus (460 BC- 370 BC) was a Greek philosopher first suggested the existence of atoms said they were indivisible and indestructible did not explain chemical behavior did not use scientific method John Dalton (1766-1844) English chemist schoolteacher used experimental methods he transformed Democritus’ ideas
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Building materials of a cell are composed of two atoms that form molecules. A chemical bond is created when two atoms share an electron. Also called covalent bond because they share valence electrons. A covalent bond‚ which is the strongest bond‚ takes action when two atoms valence overlap. For example‚ there are two suns and the light that shines from the two solid spheres forms many rays making a radiant cloud around each of the two. If these suns move closer together the radiant shine would
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things.” In other words‚ atoms are responsible for everything that is to observe in nature. Also‚ these atoms can be described more into detail with Lucretius’s four principles of atomic theory‚ his idea of an infinite universe and space in which atoms resides in‚ their combinations‚ and many more theories. All of these theories set the layout for atoms. Now‚ Lucretius focuses on atoms a lot in relation to nature‚ and to give some explanation to them‚ he describes atoms as immortal and indivisible
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from all of the atoms in the molecule or ion. • Add one electron for each unit of negative charge. • Subtract one electron for each positive charge. 2. Write the correct skeletal structure. • For molecules of the formula ABn‚ place the least electronegative element in the center‚ and the more electronegative elements in the terminal positions. • H is always a terminal atom‚ and NEVER a central atom‚ since it can only form one bond. • Draw single bonds between pair of bonded atoms. 1 Drawing Lewis
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of any substance contains the same number of atoms/molecules/ions as there are atoms in a 12g sample of carbon -12 12g of carbon-12 contains a constant number of atoms. This number is known as the Avogadro constant (L) and is equal to 6.02 x 1023. 1 mole of carbon-12 contains 6.02 x 1023 atoms. Therefore‚ 1 mole of any substance contains 6.02 x 1023 atoms/molecules/ions. For example‚ 1 mole of aluminium contains 6.02 x 1023 Al atoms 1 mole of ammonia contains 6.02 x 1023 NH3 molecules
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block an atom (meaning not divisible). Democritus believed that everything around us such as metal‚ water‚ and wood were atoms‚ but Dalton believed and proved that it could be more basic than that. He started thinking of compounds such as water‚ salt‚ or wood; that they could be a number of atoms combined to make that product. He also believed that atoms such as carbon‚ gold‚ and hydrogen could not be broken down. Dalton made some rules according to his theory: 1. All elements are made of atoms. 2.
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attraction between oppositely charged ions. Ionic bonds are formed between metals and nonmetals. Remember that metal atoms lose one or more valence electrons in order to achieve a stable electron arrangement. When a metal atom loses electrons it forms a positive ion or cation. When nonmetals react they gain one or more electrons to reach a stable electron arrangement. When a nonmetal atom gains one or more electrons it forms a negative ion or anion. The metal cations donate electrons to the nonmetal
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Module 16 Notes 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
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“WATER IS A GOOD SOLVENT” Water is very unique in all facets of its nature. The chemical formula for water is H2O as a water molecule consists of two atoms of the chemical element hydrogen (H) and one atom of the element oxygen (O). Water is the most abundant chemical compound on earth as its mass all exists together‚ naturally‚ in its gaseous‚ liquid and solid state. It is the most precious natural resource to man and is essential to life for all discovered living organisms. One of the unusual
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determine the atomic number of an atom. * Define and determine the mass number of an atom. What is an atom’s atomic number? The number of protons in the nucleus of an atom determines an element’s atomic number. In other words‚ each element has a unique number that identifies how many protons are in one atom of that element. For example‚ all hydrogen atoms‚ and only hydrogen atoms‚ contain one proton and have an atomic number of 1. All carbon atoms‚ and only carbon atoms‚ contain six protons and have
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