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02 Ch02chemistry2005 1

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  • Domains of Study Domain of BioMolecules Domain of Cells Domain of Organisms Domain of Populations Domain of Communities
  • Transcript

    • 1. Chapter 2. The Chemical Context of Life 2005-2006
    • 2. Why are we studying chemistry?
      • Biology has chemistry at its foundation
      2005-2006
    • 3.
      • Everything is made of matter
      • Matter is made of atoms
      • Atoms are made of:
        • protons + mass of 1 nucleus
        • neutrons 0 mass of 1 nucleus
        • electrons - mass <<1 orbits
      • Different kinds of atoms = elements
      The Basics 2005-2006
    • 4. The World of Elements 2005-2006
    • 5. Models of atoms 2005-2006 (c)
    • 6. Atomic structure determines behavior
      • The number of protons in an atom determines the element
        • # of protons = atomic number
        • this also tells you # of electrons
      • All atoms of an element have same chemical properties
        • all behave the same
        • properties don’t change
      2005-2006 VIDEO: Atom
    • 7. Discussion Questions
      • What is the atomic number of an atom that has 6 protons, 6 neutrons, and 6 electrons?
      • An uncharged atom of boron has an atomic number of 5 and an atomic mass of 11. How many protons does boron have?
      2005-2006
    • 8. Life requires ~25 chemical elements
      • About 25 elements are essential for life
        • Four elements make up 96% of living matter:
          • • carbon (C) • hydrogen (H)
          • • oxygen (O) • nitrogen (N)
        • Four elements make up most of remaining 4%:
          • • phosphorus (P) • calcium (Ca)
          • • sulfur (S) • potassium (K)
      2005-2006
    • 9. 2005-2006
    • 10. Isotopes
      • Different number of neutrons (heavier)
      • Some are unstable
        • nuclear reactions / decay
      • Split off neutrons &/or protons
        • radioactivity
      • Biological tool
      • Biological hazard
      2005-2006
    • 11. Discussion Question
      • Which drawing depicts the electron configuration of neon ( 20 10 Ne)?
      2005-2006
    • 12.
      • The most common form of calcium has 20 protons, 20 neutrons, and 20 electrons. Which of the following elements would be an isotope of calcium?
      • a. an atom with 20 protons, 21 neutrons, and 20 electrons
      • b. an atom with 21 protons, 20 neutrons, and 21 electrons
      • c. all of the above
      • d. an atom with 21 protons, 21 neutrons, and 21 electrons
      • e. an atom with 20 protons, 20 neutrons, and 18 electrons
      2005-2006
    • 13.
      • Effect of electrons
        • chemical behavior of an atom depends on its electron arrangement
        • depends on the number of electrons in its outermost shell, the valence shell
      2005-2006 Bonding properties How does this atom behave? VIDEO: Electron Arrangement
    • 14.
      • Effect of electrons
        • chemical behavior of an atom depends on number of electrons in its outermost shell
      2005-2006 Bonding properties How does this atom behave? How does this atom behave?
    • 15. Elements & their valence shells 2005-2006
      • Elements in the same row have the same number of shells
    • 16. Discussion Question 2005-2006 Atomic chlorine has an atomic number of 17. It has _____ electrons in its third shell.
    • 17. Elements & their valence shells 2005-2006
      • Elements in the same column have the same valence & similar chemical properties
    • 18. Discussion Question 2005-2006 Based on electron configuration, which of these elements would exhibit chemical behavior most like that of oxygen?
    • 19. Elements & their valence shells 2005-2006
      • Moving from left to right, each element has a sequential addition of electrons (and protons)
    • 20. Chemical reactivity
      • Atoms tend to
        • Complete a partially filled outer (valence) electron shell
        • or
        • Empty a partially filled outer (valence) electron shell
        • This tendency drives chemical reactions
      2005-2006
    • 21. Ionic bonds 2005-2006
    • 22. Ionic bonds
      • Transfer of an electron
      • Forms + & - ions
        • + = cation
        • – = anion
      • Weak bond
      2005-2006
      • example:
        • salt = dissolves easily in water
      Movie: Ionic Bonds
    • 23.
      • Copper has an atomic number of 29 and a mass number of 64. What would result if an uncharged copper atom lost two electrons?
      • A. The atom would have a double negative charge and be an ion.
      •  
      • B. The atomic number of the atom would remain 29, the mass number would be reduced to 62, and the atom would be an anion.
      • C. The atomic number would remain 29, the mass number would increase to 66, and the atom would be a cation with a -2 charge.
      • D. The atomic number would be reduced to 27, the mass number would remain 64, and the atom would be an anion with a +2 charge.
      • E. The atomic number would remain 29, the mass number would remain 64, and the atom would be a cation with a +2 charge.
      2005-2006
    • 24. Covalent bonds
      • Two atoms need an electron
      • Share a pair of electrons
      • Strong bond
        • both atoms holding onto the electrons
      • Forms molecules
      • example:
        • water = takes energy to separate
      2005-2006 VIDEO: Covalent Bond
    • 25. Double covalent bonds
      • Two atoms can share more than one pair of electrons
        • double bonds (2 pairs of electrons)
        • triple bonds (3 pairs of electrons)
      • Very strong bonds
      2005-2006
    • 26. Multiple covalent bonds
      • 1 atom can form covalent bonds with two or more other atoms
        • forms larger molecules
        • ex. carbon
      2005-2006
    • 27. Polar covalent bonds
      • Pair of electrons not shared equally by 2 atoms
      • Water = O + H
      2005-2006
        • oxygen has stronger “ attraction ” for the shared electrons than hydrogen
        • oxygen has higher electronegativity
      Video: Polar vs. Non-Polar
    • 28. Polar covalent bonds
      • 2 hydrogens in the water molecule form an angle
      • Water molecule is polar
        • oxygen end is –
        • hydrogen end is +
      • Leads to many interesting properties of water….
      2005-2006
    • 29. Hydrogen bonds
      • Positive H atom in 1 water molecule is attracted to negative O in another
      • Can occur wherever an -OH exists in a larger molecule
      • Weak bonds
      2005-2006 VIDEO: Hydrogen Bonds
    • 30.
      • What types of bonds are identified in the following illustration of a water molecule interacting with an ammonia molecule? Bonds 1 are polar covalent bonds, bond 2 is a hydrogen bond, and bonds 3 are nonpolar covalent bonds.
      2005-2006
        • Bonds 1 and 3 are polar covalent bonds and bond 2 is a hydrogen bond.
        • Bonds 1 and 3 are polar covalent bonds and bond 2 is an ionic bond.
        • Bonds 1 and 3 are nonpolar covalent bonds and bond 2 is a hydrogen bond.
        • d)Bonds 1 and 3 are polar covalent bonds and bond 2 is a nonpolar covalent bond.
        • e) Bonds 1 and 3 are polar covalent bonds and bond 2 is a nonpolar covalent bond
    • 31. Reductionist view of biology
      • Matter is made of atoms
      • Life requires ~25 chemical elements
      • Atomic structure determines behavior of an element
      • Atoms combine by chemical bonding to form molecules
      • Weak chemical bonds play important roles in chemistry of life
      • A molecule’s biological function is related to its shape
      • Chemical reactions make & break chemical bonds
      2005-2006
    • 32. Any Questions?? 2005-2006

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