LS2_Ch2Outline - Chapter 2 The Chemistry of Life 2.1 What...

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Chapter 2: The Chemistry of Life 2.1: What are the chemical elements that make up living organisms? All matter is composed of atoms. - Each consists of: Dense, positively charged nucleus that contains protons and may contain neutrons. Negatively charged electrons that move around the nucleus. - Have volume and mass (measures the quantity of matter present). - Atomic mass unit (amu)/dalton: standard unit of measure. Proton (+) or neutron ( ) = 1 dalton (Da) = 1.7x10 -24 grams Electron (-) = 0.0005 Da = 9x10 -28 g (negligible mass, but determines how atoms interact in chemical reaction. - Unlike charges (+/-) attract, like charges (+/+, -/-) repel. - Atoms are neutral; number of electrons equals number protons. I. Element: pure substance that contains only one kind of atom. A. Atoms of each element have certain characteristics that distinguish them from atoms of other elements. B. >100 elements; arranged in periodic table. C. Elements are not found in equal proportions. D. ~98% mass of every living organism is composed of: carbon, hydrogen, nitrogen, oxygen, phosphorous, and sulfur. E. Other elements/ trace elements are also important: 1. Sodium and potassium : essential for nerve function. 2. Calcium : can act as a biological signal. 3. Iodine : component of a vital hormone. 4. Magnesium : part of chlorophyll pigment in plants. 5. Molybdenum : incorporates nitrogen into biologically useful substances in plants. II. Protons: Their number identifies an element A. Atomic number: definitive number of protons in each atom of an element. B. Every element except hydrogen has one or more neutrons in its nucleus. C. Mass number: total number of protons and neutrons in an atom’s nucleus; mass of atom in Daltons. D. Preceding element symbol, atomic number in written in the lower left and mass number in the upper left. (eg. 1 1 H, 12 6 C) III. Neutrons: Their number differs among isotopes A. Isotopes: differ in number of neutrons. B.
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LS2_Ch2Outline - Chapter 2 The Chemistry of Life 2.1 What...

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