GEN CHEM CHP 3 MCAT REVIEW Flashcards


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created 11 days ago by cocordrgz
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1

bonding

molecules - atoms held together by attractive force: chem bonds by valence e- interactions

octet rule - atoms tend to bond so they both have 8 valence e-

  • exceptions:
  • incomplete octet:
    • H (2)
    • helium (2)
    • Li (2)
    • Be (4)
    • Boron (6)
  • expanded: any element period 3/more
  • odd # e-: like NO (nitric oxide) (7)

ionic bonds - 1/more e- from atom w/ low IE transferred to atom w/ high e- affinity (usually metal/nonmetal)

covalent bonds - e- shared btw 2 atoms (usually nonmetals) w/ similar electronegativity

polar or nonpolar

2

ionic bonds

ionic bonds - form btw atoms w/ very diff EN

  • high MP / BP
  • dissolve readily in water/polar solvents
  • molten/aq. = good conductor of electricity
  • forms crystalline lattice
3

covalent bonds - properties

  • atoms joined by 1/multiple pairs e-
    • single, double, triple covalent bond has 1, double bond, triple bond respectively shared
    • bond order - # shared e- btw 2 atoms
    • explain by 3 characteristics
      • bond length - avg distance btw 2 nuclei of atoms in bond
        • 3x bond < 2x bond < 1x bond
      • bond energy - energy to break bond
        • 3x > 2x > 1x
      • polarity - when have diff EN
        • higher EN = higher e- density
        • nonpolar covalent bond - same EN share e- equally
          • H2, N2, O2, F2, Cl2, Br2, I2
        • polar covalent bond - share e- unevenly. cause partial neg/pos charges on atoms + creates dipole moments
4

coordinate covalent bond

coordinate covalent bond - shared e- all came from same atom

5

lewis dot diagram

lewis dot diagram

  • least EN atom in center (NEVER H + not usually halogens)
  • draw single bonds from center to adjacent atoms
  • complete octets of all atoms boounded to central one
  • put extra e- on center atom (if not enough, make 2x/3x bonds from central atom to others)
6

formal charge

formal charge - valence - electrons - bonds

7

VSEPR

card image

VSEPR

  • electron geometry - (based on electrons) assume geometry without accounting for lone pairs
  • molecular geometry - actual geometry based on lone pairs present
8

molecule polarity

use molecular geometry to know if dipoles cancel or not

(remember dipoles CANNOT cancel if is able to rotate (single bond) in a way that it wouldnt cancel

9

LDF

london dispersion forces LDF - at any point in time, e- located randomly and may be unequally distributed in a molecule, causeing momentary positive and negative ends = attractive/repulsive interactions

  • weakest IM force
  • only work if molecules close
10

dipole-dipole interactions

dipole-dipole interactions - in solid/liquid (not really gas)

  • higher MP/BP bc of polarity
11

H bonds

H bonds - type of dipole dipole interaction

  • intra/intermolecular
  • when H bonds to FON atoms
  • strongest = highest BP/MP bc most polar