Chapter 2 The Chemical Context of Life

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Chapter 2The Chemical Context of Life
2
Atoms

• Subatomic particles
• protons (p)
• neutrons (n)
• electrons (e)

3
Electromagnetic charges

• p 1
• n neutral
• e -1

4
Mass of subatomic particles

• 1 dalton 1.67 X 10-24 g
• p 1 dalton
• n 1 dalton
• e 1/2000 dalton

5
Relationships

• Atomic of protons
• 8O
• mass protons n 16O

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Isotope

• The atomic form of an element with different
  number of neutrons
• Three isotopes of C
• 12C 6p 6 n
• 13C 6p 7n
• 14C 6p 8n

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Ions

• Atoms that have gained or lost electrons

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Cations and Anions

• lost electron cation
• Na 11p 11e 11n
• Na 11p 10e 11n
• gain electron anion
• Cl 17p 17e 17n
• Cl - 17p 18e 17n

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Chemical Reaction

• Reactants -------gt products

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Redox Reaction

• Chemical reaction involving the transfer of 1 or
  more electrons from one reactant to another
• Red reduction, gain of electrons by a substance
• ox oxidation, loss of electrons by a substance

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Redox Reactions

• Tip
• LEO the GERMAN
• lose electrons oxidation
• gain electrons reduction

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Redox Reaction

• C6H12O6 6O2 --gt 6CO2 6H2O
• ox red
• reducing oxidizing agent agent

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Energy Levels

• Electron orbitals
• space around nucleus where electrons are most
  likely to be found (90 of the time)
• can be shaped differently
• Shells
• energy levels within an orbital

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Electron Shells

• Outermost shell determines behavior of atom
• Valence electrons
• electrons in the outermost shell (valence shell)
• Octet Rule
• valence shell complete with 8 electrons (except
  H, He)

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Chemical Bonds

• Examine three types
• covalent bond
• ionic bond
• hydrogen bond

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Covalent Bond

• Sharing of electron pairs
• single bonds
• double bonds
• triple bonds
• covalent bonds
• nonpolar covalent bonds
• polar covalent bonds

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Ionic Bond

• Attraction between ions of opposite charge

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Hydrogen Bond

• A slightly positive H atom of a polar covalent
  bond in one molecule is attracted to a slightly
  negative atom of a polar covalent bond in another
  molecule

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Essential Elements to Life

• 25 of the 92 naturally occurring elements are
  essential to life
• 4 (C, O, H, N) make up 96 of living matter

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Essential Elements

• C 18.5
• H 9.5
• O 65
• N 3.5
• total 96.5 of living matter

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Essential Elements

• 3.5
• Ca, P, K, S, Na, Cl, Mg,
• trace elements (lt0.01 each)
• required in minute amounts
• B, Cr, Co, Cu, F, I, Fe, Mn, Mo, Se, Si, Sn, V,
  Zn

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Chapter 2

• THE END