model of atoms (1900)– negative electrons in a positive framework 1800‚ John Dalton‚ English chemist: • Proposed the atomic patterns‚ which account for the law of conservation of mass and the law of constant composition • All matter is made of atoms; atoms of an element are identical; each element has different atoms; atoms of different elements combine in constant ratios to form compounds; atoms are rearranged in reactions. • “Billiard ball’ model – atoms are solid
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Checkpoint questions Chapter 2 1. Define atom Atom is the smallest stable units of matter 2. Atoms of the same element that have different numbers of neutrons are called _______. isotopes 3. How is that possible for two samples of hydrogen to contain the same number of atoms‚ yet have different weights? Exactly two atoms of hydrogen combine with one atom of oxygen. But individual atoms are far too small and too nomerous to be counted‚ so chemists use a unit
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Short Notes On Atomic Structure * Atom is the smallest particle of an element- All 117 elements has atoms * Bohr model: - Planetary model (see Figure 1 below) 1. Sun (proton & neutron= nucleus) 2. Planets (electrons) 3. Orbit (shell) Figure 1: Bohr model * Each type of atoms has a certain number of electrons and protons that differentiate it from the atoms of other elements Example: 1 proton 1 electron= Hydrogen (1 type elements) 2
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Molecular Geometry The specific three dimensional arrangements of atoms in molecules are referred to as molecular geometry. We also define molecular geometry as the positions of the atomic nuclei in a molecule. There are various instrumental techniques such as X-Ray crystallography and other experimental techniques which can be used to tell us where the atoms are located in a molecule. Using advanced techniques‚ very complicated structures for proteins‚ enzymes‚ DNA‚ and RNA have been determined
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6 + (7*2) = 20 The answer is “d” because it does not have eight valence electrons. 64) Explain why each electron structure is incorrect. Replace each structure with one that is more acceptable. a) It is incorrect because neither of the atoms follow the octet rule and doesn’t add up to a correct charge. They don’t have any bonds either. b) The Lewis dot structure doesn’t follow the octet rule‚ have the correct number of electrons‚ or any bonds. 74) Ethyl alcohol
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involves the sharing of pairs of electrons between atoms. A compound is made when two or more atoms form a chemical bond‚ linking them together. The two types of bonds are ionic bonds and covalent bonds. In an ionic bond‚ the atoms are bound together by the attraction between oppositely charged ions. If the electron is shared equally between the atoms forming a covalent bond‚ then the bond is said to be nonpolar. An electron is more attracted to one atom than to another which forming a polar covalent
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experimental evidences for i) strong repulsive force ii) strong attractive force between atoms in a solid. (b) A simple model for the oxygen molecule consists of two equal masses connected by a light spring . The atoms oscillate along their lines of centre while the midpoint of the spring remains fixed. i) Write down an expression for the frequency of oscillation of one oxygen atom in terms of its mass m and the force constant K of one half of the spring. How is K related to the force
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POWER ATOM TV SUBMITTED BY DEWESH J RR 1908 A 21 SUBMITTED TO SAVITA MAM L S B MARKETING PLAN OF POWER ATOM The marketing plan
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Rutherford spent his life studying radioactive elements and their importance to our world. Rutherford made the groundbreaking discovery that nearly the total mass of an atom is concentrated in a nucleus.He also found that radioactive elements have "half-lives." In so doing‚ he gave birth to the nuclear model‚ a discovery that marked the inception of nuclear physics‚ leading to his win of the Nobel Prize in Chemistry. This
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class with the periodic table. 2. Johnny couldn’t find Sodium Chloride on the periodic table because Sodium Chloride is a molecule made up of two atoms: Sodium and Chloride. 3. Sodium Chloride represents two atoms that together form a molecule: NaCl. Na: Sodium and Cl: Chloride 4. An ionic bond occurs when two or more ions (an atom whose number of elections differs from its number of protons) bond together because of their opposite charge. They are drawn to each other like magnets
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