Bonding & Organic Chemistry: Quick Notes (Last-Minute)

Covalent and Ionic Bonds

  • Ionic bond: electron transfer → oppositely charged ions; strong electrostatic attraction; high melting/boiling points; typically solid at room temperature.
  • Covalent bond: atoms share electrons; intramolecular bond within molecules; bonding between nonmetals.
  • Intermolecular forces exist for both types; stronger in ionic systems; weaker between covalent molecules (Van der Waals).\
    • Van der Waals force = intermolecular force between covalent molecules (named after Van der Waals).
    • Intermolecular electrostatic forces in ionic compounds are strong (due to full charges).
  • Summary: ionic = transfer + electrostatic attraction; covalent = sharing + weaker intermolecular forces.

Giant Covalent vs Simple Covalent

  • Simple covalent compounds: discrete molecules held together by covalent bonds; weaker intermolecular forces.
  • Giant covalent compounds (GCC): extended network of covalent bonds (no discrete molecules).
  • Examples of GCC:
    • Diamond: each C forms 4 covalent bonds to carbon neighbors (tetrahedral network); very high mp/bp; extremely hard; does not conduct electricity.
    • Graphite: C atoms form layers of hexagons; each C bonds to 3 others; one extra electron per C → conducts electricity along layers; layers held by weaker interlayer forces; layers can slide; mp high; relatively soft along planes.
    • Silicon dioxide (SiO$_2$): another GCC example; network solid with strong covalent bonds.

Graphite conduction detail

  • Conductivity:Graphite conducts electricity along the layers because of delocalized electrons; cannot conduct well between layers.
  • Physical properties: high mp; layers allow sliding (lubricating); direction-dependent conductivity.

Metallic Bond

  • Metallic bond: sea of delocalized electrons around metal cations; enables electrical conductivity and malleability.

Carbon and Organic Chemistry Basics

  • Carbon is the main element in organic chemistry; valence = 44; forms four bonds.
  • Prefixes by carbon count (for chain length):
    • 1
      ightarrow ext{meth-}, 2
      ightarrow ext{eth-}, 3
      ightarrow ext{prop-}, 4
      ightarrow ext{but-}, 5
      ightarrow ext{pent-}
  • Suffixes for bonding type:
    • −ane-ane: single bonds (alkanes)
    • −ene-ene: presence of a double bond (alkenes)
    • −yne-yne: presence of a triple bond (alkynes)
    • −ol-ol: alcohol group
  • Bond drawing conventions:
    • Beginner level: one covalent bond drawn as a single line.
    • Organic chemistry level: each bond is represented by lines; single line = one shared electron pair; double line = two electron pairs; triple line = three electron pairs.
  • Carbon’s bonding tendency:
    • Carbon needs four bonds to be stable (valence 4).
    • Hydrogen needs one bond (valence 1).
    • Oxygen typically needs two bonds (valence 2).
  • Carbon as the backbone: focus on carbon as the central element in organic molecules; many groups and functional groups build on carbon skeletons.

Quick drawing reminders (from today’s walkthrough)

  • How to convert beginner drawing to organic-level drawing:
    • 1 line between atoms = 1 bond (1 electron pair)
    • 2 lines between atoms = 2 bonds (2 electron pairs) (double bond)
    • 3 lines between atoms = 3 bonds (3 electron pairs) (triple bond)
  • The syllabus typically uses up to triple bonds in basic examples; most common cases show up to two bonds in simple molecules.

Practice focus

  • Copy these notes; draw examples for meth-, eth-, prop-, but-, pent- chains; label simple alkanes, alkenes, alkynes, and an alcohol (e.g., methanol).
  • Remember the three GCC examples: Diamond, Graphite, SiO$_2$.