C1.2 Chemical Bond & its Characteristics

Semester 1: Foundation of Basic Science
Case 1: Chemistry of Life
Obj 2: Chemical Bond & its Characteristics

Chem Bonds =divided into two (Intramolecule / Intermolecule)

• Intramolecular bond

1) Covalent

- a bond between non metal + non metal by sharing electron to achieve stable electronic configuration

- electron shared = no of bonds
- < 1.7 difference electronegativity (less ionic)

• Polar = when atom is more electronegative than another
• Non-polar = when electron equally shared

2) Ionic (electrostatic forces)
- a bond between metal (low e) + non metal (high e) by electron transfer
- > 1.7 difference electronegativity (more ionic)
- cation (+ ion) / anion (- ion)

3) Metallic
- a bond between metal + metal in crystal lattice
- have low ionization energy (so electron move around n act as cement that hold metal ions)
- lustrous / malleable / ductile

• Intermolecular Bond

1) Hydrogen bond

- electrostatic attraction between an electronegative atom (O / N) + a hydrogen atom that is covalently bonded to 2nd electronegative atom

- increase electronegativity of atom bounded to hydrogen = increase bond strength

-can be either intermolecular o intramolecular

2) Van der Waals

-short-range forces / between molecules or parts of molecules / where atoms attract when they are at certain distance / and repel when the atoms approach (tendency to maintain distance)

-more significant when (increase pressure / decrease temperature)

3)Hydrophobic Attraction / Interaction (Molecule - Ion Interaction)
-Interaction / between non-polar side chain molecule / and other non-polar side chain molecule / which tend to aggregate minimizing surface area exposed to water (to avoid water molecules) / allowing these molecules to associate with each other in aqueous environment