human phys _ 1%2F2%2F18.docx

human phys _ 1%2F2%2F18.docx - I Atomic Structure of...

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I. Atomic Structure of Elements Elements are composed of Nucleus [Protons (+ charge) and Neutrons] Electrons (- charge) Atomic Number = number of protons Mass Number = number of protons and neutrons Elements are electrically neutral they have the same number of protons and electrons To determine the # of Neutrons Mass Number – Atomic Number The body has 4 primary elements: “CHON” – composes ~96% of the body’s weight Carbon Hydrogen Oxygen Nitrogen Other element: Calcium (bones) can be included to make up ~99% of the body’s weight Hydrogen Atomic Number = 1 Mass Number = 1 (1 proton, 0 neutrons) Carbon AN = 6 (6 e - : 2 in 1 st orbital, 4 in 2 nd ) MM = 12 (6 protons, 6 neutrons) Nitrogen AN = 7 (7 e -: 2 in 1 st orbital, 5 in 2 nd ) MN = 14 (7 protons, 7 neutrons) Oxygen AN = 8 (8 e - : 2 in 1 st orbital, 6 in 2 nd ) MN = 16 (8 protons, 8 neutrons) 2 electrons allowed in first orbital, 8 in others Types of Bonds Max number of electrons in the 1 st orbital is 2. Max number of electrons in all subsequent orbitals is 8 (octet rule). All elements would like the outermost orbital filled with the max number of electrons. This can give rise to different types of bonds.
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Covalent Bonds Atoms share electrons Ex: Oxygen can share e - with 2 H Outer orbitals for all the elements (i.e O and 2H) are filled. Oxygen does not share electrons equally - the electrons will spend most of the time around the oxygen. This gives rise to partial negative charges around the oxygen and partial positive charges around the hydrogens. Unequal sharing gives rise to polar molecules 60% of body weight is water Cells are “bathed” in water, i.e. there is water inside cells and outside cells Ionic Bonds Opposite charges attract [Na + Cl - ] Sodium [Na] AN = 11 (11e - ) [In orbitals: 2,8,1]- will lose one e - in the outer orbital making it positive MN = 23 (11 protons, 12 neutrons) Chloride [Cl] AN = 17 (17e - ) [In orbitals: 2,8,7]- will gain one e - in the outer orbital making it negative MN = 35 (17 protons, 18 neutrons) Polar molecule !! will dissolve in water
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