C2 ppt

• Matter


  Anything that takes up space and has mass
• Atoms


  The smallest chemical units of matter
• Atomic Structure


  • Electrons - negatively charged subatomic particles circling a nucleus
  • Nucleus - structure containing neutrons and protons
  • Neutrons - uncharged particles
  • Protons - positively charged particles

  
• Element


  Composed of a single type of atom
• Atomic number


  Equal to the number of protons in the nucleus
• Atomic mass (atomic weight)


  Sum of masses of protons, neutrons, and electrons
• Isotopes


  Atoms of a given element that differ in the number of neutrons in their nuclei
• Types of isotopes


  • Stable isotopes
  • Unstable isotopes
  • Radioactive isotopes
• Radioactive isotopes release energy during radioactive decay
• Electron Configurations


  • Only the electrons of atoms interact, so they determine atom's chemical behavior
  • Electrons occupy electron shells
  • Valence electrons - electrons in outermost shell that interact with other atoms
• Electron shells of neon

  • Three-dimensional view
  • Two-dimensional view
• Electrons zip around the nucleus at about 5 million miles per hour. Why don't some fly off?
• Valence


  • Combining capacity of an atom
  • Positive if atom has electrons to give up
  • Negative if atom has spaces to fill
  • Stable when outer electron shells contain eight electrons
• Chemical bonds


  Atoms combine by sharing or transferring valence electrons
• Molecule


  Two or more atoms held together by chemical bonds
• Compound


  A molecule composed of more than one element
• Covalent bond


  Sharing of a pair of electrons by two atoms
• Electronegativity


  • Attraction of atom for electrons
  • The more electronegative an atom, the greater the pull its nucleus exerts on electrons
• Nonpolar Covalent Bonds


  • Shared electrons spend equal amounts of time around each nucleus
  • Atoms with similar electronegativities
  • No poles exist
  • Carbon atoms form four nonpolar covalent bonds with other atoms
• Molecules formed by covalent bonds

  • Four examples
• Polar Covalent Bonds


  • Unequal sharing of electrons due to significantly different electronegativities
  • Most important polar covalent bonds involve hydrogen
  • Allow for hydrogen bonding
• Ionic Bonds


  • Occur when two atoms with vastly different electronegativities come together
  • Atoms have either positive (cation) or negative (anion) charges
  • Cations and anions attract each other and form ionic bonds (no electrons shared)
  • Typically form crystalline ionic compounds known as salts

  
• Hydrogen Bonds


  • Electrical attraction between partially charged H+ and full or partial negative charge on same or different molecule
  • Weaker than covalent bonds but essential for life
  • Help to stabilize 3-D shapes of large molecules

  
• Chlorine and potassium atoms form ionic bonds, carbon atoms form nonpolar covalent bonds with nitrogen atoms, and oxygen forms polar covalent bonds with phosphorus. Explain why these bonds are the types they are.

  
• Chemical Reactions


  • The making or breaking of chemical bonds
  • Involve reactants and products
  • Biochemistry involves chemical reactions of living things

  
• Synthesis Reactions


  • Involve the formation of larger, more complex molecules
  • Require energy (endothermic)
  • Common type is dehydration synthesis
  • Water molecule formed
  • All the synthesis reactions in an organism are called anabolism
• Decomposition Reactions


  • Break bonds within larger molecules to form smaller atoms, ions, and molecules
  • Release energy (exothermic)
  • Common type is hydrolysis
  • Ionic components of water are added to products
  • All the decomposition reactions in an organism are called catabolism

  
• Exchange Reactions


  • Involve breaking and forming covalent bonds
  • Have endothermic and exothermic steps
  • Atoms are moved from one molecule to another
  • Sum of all chemical reactions in an organism is called metabolism
• Why are decomposition reactions exothermic (release energy)?
• Water


  • Most abundant substance in organisms
  • Many special characteristics due to two polar covalent bonds
  • Cohesive molecules - surface tension
  • Excellent solvent
  • Remains liquid across wide range of temperatures
  • Can absorb significant amounts of energy without changing temperature
  • Participates in many chemical reactions
• Acids and Bases


  • Dissociated by water into component cations and anions
  • Acid - dissociates into one or more H+ and one or more anions
  • Base - binds with H+ when dissolved into water; some dissociate into cations and OH-
  • Concentration of H+ in solution expressed using the pH scale
  • Metabolism requires relatively constant balance of acids and bases
  • Buffers prevent drastic changes in internal pH
  • Microorganisms differ in their tolerance of various pH ranges
  • Some microbes can change the pH of their environment

  
• Salts


  • Compounds that dissociate in water into cations and anions other than H+ and OH-
  • Cations and anions of salts are electrolytes
  • Create electrical differences between inside and outside of cells
• Acids


  Dissociated by water into component cations and anions
• Acid


  Dissociates into one or more H+ and one or more anions
• Base


  Binds with H+ when dissolved into water; some dissociate into cations and OH–
• pH scale


  Concentration of H+ in solution expressed using
• Metabolism requires relatively constant balance of acids and bases</b>
• Buffers


  Prevent drastic changes in internal pH
• Microorganisms


  • Differ in their tolerance of various pH ranges
  • Some can change the pH of their environment
• Salts are compounds that dissociate in water into cations and anions other than H+ and OH–