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Chapter 2: The Chemical Context of Life

Chapter 2: The Chemical Context of Life. Chemical Context of Life. Matter (space & mass) Element Compound The atom Atomic number (# of protons); mass number (protons + neutrons) Isotopes (different # of neutrons); radioactive isotopes (nuclear decay)

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Chapter 2: The Chemical Context of Life

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  1. Chapter 2: The Chemical Context of Life

  2. Chemical Context of Life • Matter (space & mass) • Element • Compound • The atom • Atomic number (# of protons); mass number (protons + neutrons) • Isotopes (different # of neutrons); radioactive isotopes (nuclear decay) • Energy (ability to do work); energy levels (electron states of potential energy)

  3. Chemical Bonding • Covalent • Double covalent • Nonpolar covalent • Polar covalent • Ionic • Hydrogen • van der Waals

  4. Covalent Bonding • Sharing pair of valence electrons • Number of electrons required to complete an atom’s valence shell determines how many bonds will form • Ex: Hydrogen & oxygen bonding in water; methane

  5. Covalent bonding

  6. Polar/nonpolar covalent bonds • Electronegativity attraction for electrons • Nonpolar covalent •electrons shared equally •Ex: diatomic H and O • Polar covalent •one atom more electronegative than the other (charged) •Ex: water

  7. Polar/nonpolar bonds

  8. Ionic bonding • High electronegativity difference strips valence electrons away from another atom • Electron transfer creates ions (charged atoms) • Cation (positive ion); anion (negative ion) • Ex: Salts (sodium chloride)

  9. Ionic bonds

  10. Hydrogen bonds • Hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom (oxygen or nitrogen)

  11. Hydrogen bonds

  12. van der Waals interactions • Weak interactions between molecules or parts of molecules that are brought about by localized change fluctuations • Due to the fact that electrons are constantly in motion and at any given instant, ever-changing “hot spots” of negative or positive charge may develop

  13. van der Waals interactions

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