Bio Chap 2

Bio Chap 2 - Chapter2 Atoms,Molecules&Life Elements n n

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Chapter 2 Atoms, Molecules & Life
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Elements n Form all matter either together or alone n Pure chemical substance consisting of only one  type of atom n                 subatomic particles within the atoms n Can be:  n Gases, liquids or solids  n Highly reactive or inert  n Essential to living organisms 
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96% Total  
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Atoms n Fundamental structural units of elements  n Retain all properties of elements n Composed of 3 subatomic particles: n    Protons = positively charged n    Neutrons = uncharged n Prevent protons from repelling each other  n Present in all elements except hydrogen  n Electrons = negatively charged    n Orbit nucleus within electron shells  n n In general: atoms are electrically nuetral  n # of protons (+) =   # of electrons (-)                   Make up the
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(a) Hydrogen (H) electron shell atomic nucleus e p (b) Helium (He) n n e p p e Atomic Models (fig 2-1)
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Periodic Table of Elements n Organizes elements by their: n Atomic number = number of protons  n All atoms of same element have same atomic # n Ex: Hydrogen: 1 proton -> atomic # = 1  n Ex: Carbon: 6 protons -> atomic # = 6  n  Chemical properties n Each element also has: n A specific chemical symbol  n An  atomic mass    n Total mass of  protons, neutrons, & electrons
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Isotopes n Atoms of same element that vary in number of neutrons   n Most are stable  n Some are radioactive  n  Spontaneously break apart to form different atoms n Release energy  n tests   n Ex: Positron Emission Tomography (PET scans) n Detect brain tumors using radioactive isotopes of fluorine n Tumor cells emit high levels of energy n Tumor shows up as a “hot spot” on an image
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Carbon (C) Oxygen (O) Phosphorus (P) Calcium (Ca) Ca O C P 4 e 6 e 5 e 2 e 8 e 8 e 8 e 2 e 2 e 2 e 2 e 6 p 8 p 15 p 20 p 6 n 8 n 16 n 20 n Electron shells of atoms n Electrons orbit nucleus within electrons shells 
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Bio Chap 2 - Chapter2 Atoms,Molecules&Life Elements n n

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