General Biology Inorganic Chemistry I. Chemical Elements and Compounds



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General Biology

I. Chemical Elements and Compounds

  • I. Chemical Elements and Compounds
  • A. Elements
    • Consist of only one kind of atom, cannot be decomposed into a simpler substance.
    • The planet is made up of some 90 elements.
    • Only 25 or so are used to build living things.
    • All matter is made of elements.

Consider the following chart.

    • Consider the following chart.
  • Elemental composition of the lithosphere and the human body. Each number represents the percent of the total number of atoms present.
  • Composition of Lithosphere Composition of the Human Body
  • Oxygen
  • 47
  • Hydrogen
  • 63
  • Silicon
  • 28
  • Oxygen
  • 25.5
  • Aluminum
  • 7.9
  • Carbon
  • 9.5
  • Iron
  • 4.5
  • Nitrogen
  • 1.4
  • Calcium
  • 3.5
  • Calcium
  • 0.31
  • Sodium
  • 2.5
  • Phosphorous
  • 0.22
  • Potassium
  • 2.5
  • Chlorine
  • 0.08
  • Magnesium
  • 2.2
  • Potassium
  • 0.06
  • Titanium
  • 0.46
  • Sulfur
  • 0.05
  • Hydrogen
  • 0.22
  • Sodium
  • 0.03
  • Carbon
  • 0.19
  • Magnesium
  • 0.01
  • All others
  • <0.1
  • All others
  • <0.01

Living Matter

    • Living Matter
      • Uses only a fraction of the elements available to it.
      • The relative proportions of those it does acquire from its surroundings are quite different from the proportions in the environment.
      • One of the properties of life is to take up certain elements that are scarce in the nonliving world and concentrate them within living cells.
      • C, O, H, & N make up 96% of living matter

B. Atoms consist of protons, neutrons, and electrons

    • B. Atoms consist of protons, neutrons, and electrons

Drawing Atoms

  • Drawing Atoms
  • Draw the following atoms, showing all subatomic particles.
  • Helium (He)
  • Lithium (Li)
  • Fluorine (F)

II. Isotopes

  • II. Isotopes
    • Atoms of an element that have the same atomic number but different mass number.
    • Elements occur as mixtures of isotopes.
    • Different isotopes of the same element react chemically in the same way. Why?
    • Some isotopes are radioactive.
    • Unstable isotope in which the nucleus spontaneously decays, emitting subatomic particles and/or energy as radioactivity.
    • Biological applications of radioactive isotopes:
      • Dating geological strata and fossils (Radioactive decay is at a fixed rate)
  • http://earthsci.org/geotime/radate/radate.html#Radiocarbon
  • January 12, 2004

2. Radioactive tracers (Used to study biological pathways)

      • 2. Radioactive tracers (Used to study biological pathways)
      • 3. P, N, and H were used to determine DNA structure
      • 4. Treatment for some cancers (Cobalt)
      • 5. Can be extremely hazardous to cell molecules
      • 6. Used to diagnose disease (PETscanner)
  • http://www.triumf.ca/welcome/petscan.html
  • January 12, 2004

III. Compounds

    • III. Compounds
    • A pure substance composed of two or more elements combined in a fixed ratio.
    • Example: NaCl (sodium chloride)

IV. Electron Configuration

  • IV. Electron Configuration
    • An atom’s electron configuration determines its chemical behavior.
    • Chemical properties of an atom depend upon the number of valence electrons.
    • The valence electrons are responsible for the atom’s bonding capacity (Octet Rule)

V. Bonding

  • V. Bonding
    • Chemical Bonds – Attractions that hold molecules together.
    • Molecules – Two or more atoms held together by chemical bonds.

A. Covalent Bonds

    • A. Covalent Bonds
    • Chemical bond between atoms formed by sharing a pair of valence electrons.
    • Strong chemical bond
  • Illustrate covalent bonding;
  • Hydrogen and Hydrogen

Covalent Bonding Continued

    • Covalent Bonding Continued
    • Two types, nonpolar covalent and polar covalent bonds.
    • The electronegativity is the atoms ability to attract and hold electrons.
    • The more electronegative an atom, the more strongly it attracts shared electrons.
    • Notice that Fluorine is the most electronegative, but it is Oxygen that is exploited by life.
    • The relative electronegativity of two interacting atoms plays a major part in determining what kind of chemical bond forms between them.

1. Nonpolar Covalent Bond – Covalent bond formed by an equal sharing of electrons between atoms.

  • 1. Nonpolar Covalent Bond – Covalent bond formed by an equal sharing of electrons between atoms.
      • Occurs when electronegativity of both atoms is about the same.
      • Molecules made of one element.
    • Illustrate Nonpolar Covalent Bonding;
    • Carbon and Hydrogen

2. Polar Covalent Bond – Covalent bond formed by an unequal sharing of electrons between atoms.

    • 2. Polar Covalent Bond – Covalent bond formed by an unequal sharing of electrons between atoms.
      • Occurs when the atoms involved have different electronegativities.
      • Shared electrons spend more time around the more electronegative atom.
      • Think of it as a Tug-Of-War
    • Oxygen e Hydrogen
    • Oxygen e Hydrogen

B. Ionic Bonds

  • B. Ionic Bonds
    • Bonds formed by the electrostatic attraction after the complete transfer of an electron(s) from one atom to another.
    • Ion – Charged atom or molecule
    • Anion – An atom that has gained one or more electrons from another atom and has become negatively charged.

Cation – An atom that has lost one or more electrons and has become positively charged.

    • Cation – An atom that has lost one or more electrons and has become positively charged.
    • Ionic Compounds are called salts.
    • A strong chemical bond.

C. Weak Chemical Bonds

  • C. Weak Chemical Bonds
  • 1. Hydrogen Bonds – bond formed by the charged attraction when a hydrogen atom covalently bonded to one electronegative atom is attracted to another electronegative atom.
      • About 20 times easier to break than a covalent bond.

2. Van der Waals Interactions – weak interactions that occur between atoms and molecules that are very close together and results from charge asymetry in electron clouds.

      • 2. Van der Waals Interactions – weak interactions that occur between atoms and molecules that are very close together and results from charge asymetry in electron clouds.
    • 3. Weak Bonds play important roles in the chemistry of life.
      • Make chemical signaling possible in living organisms (short lived responses)
      • Help stabilize the three-dimensional shape of large molecules.

VI. Structure and Function

  • VI. Structure and Function
    • A molecule has a characteristic size and shape.
    • The function of a molecule is dependent upon the shape of the molecule.
    • Example: Insulin causes glucose uptake into liver and muscle cells of vertebrates because the shape of the insulin molecule is recognized by specific receptors on the target cell.

VII. Chemical Reactions

  • VII. Chemical Reactions
    • Process of making and breaking chemical bonds leading to changes in the composition of matter.
    • Reactants undergo changes to become products.
    • Most reactions are reversible.
    • Chemical equilibrium – equilibrium established when the rate of forward reaction equals the rate of reverse reaction.

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