Bio 9-Ch 2 Lect 1 Nature of Matter fill in.ppt

18 backbone of organic molecules hydrogen 10

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– 18% - backbone of organic molecules hydrogen – 10% - component of water, in most organic compounds nitrogen – 3% - component of all proteins, DNA calcium – 1.5% component of teeth, bones, need for muscle contraction, nerve impulses Phosphorus – 1% - needed for DNA
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o Atomic number = the number of protons in the nucleus of an element = the number of protons and electrons o Atomic number of carbon (C) is 6 o Each (C) has 6 protons and 6 electrons
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o Atomic mass= total number of protons and neutrons in the nucleus of an atom To get the number of neutrons : subtract the atomic # from the mass #
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ISOTOPES o Isotopes = atoms of the same element that have a different number of neutrons o Example -- although all atoms of carbon have 6 protons , some have 6 neutrons, some 7, and a few have 8 o Elemental isotopes have the same number of electrons—all have the same chemical properties
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o Radioactive isotopes = nuclei are unstable and break down at a constant rate over time o Radiation can be dangerous BUT radioactive isotopes have important scientific and practical uses o Geologists can determine the ages of rocks and fossils by analyzing their isotopes o Radiation from certain isotopes are used to detect and treat cancer , and kill bacteria o Radioactive isotopes are used as labels or “tracers” to follow the movements of substances within organisms
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Chemical compound = a substance formed by the chemical combination of 2 or more elements
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