Atoms bond to lower their vibrational energy (complete an octet)

Electronegativity is the tendency of an atom’s nucleus to attract electrons in a covalent bond

VSEPR--- Valence Shell Electron Pair Repulsion

Dipoles have partial charges

“Like dissolves like”

Types of Bonds

Covalent

• shared electrons

• polar--- charge is shared unevenly (creates dipoles)

• nonpolar--- charge is shared evenly

• low melting point, non-conductor, particles are called molecules

• Ex: H2O

Ionic

• transferred electrons

• 2 ions with opposite charges (Electrostatic Attractions)

• high melting point, conductor when melted/dissolved (non-conductor when solid), particles are called formula units

• Ex: NaCl

Metallic

• delocalized electron “sea”

• metallic properties stay (conductivity, luster, malleability, high melting point)

Octet Rule

• Hydrogen--- 2 electrons stabilize

• Beryllium--- 4 electrons stabilize

• Boron & Aluminum--- 6 electrons stabilize

• Elements larger than aluminum can share >8 electrons (empty d-orbital)

• C, Si, & O can double/triple bond

Intramolecular forces

London Dispersion Forces

• caused by momentary polarization of electron clouds

• instantaneous dipole induces a dipole on a nearby molecule

• short-range, between nonpolar molecules

Dipole-Dipole Forces

• positive dipole aligns with negative dipole

• increased strength with increased polarity

• molecules must be close together and polar

LDF + dipole-diple = van der Waals

Hydrogen Bonding

• hydrogen covalently bonds to a negative element with a lone pair

• other element must be oxygen, nitrogen, or fluorine

• causes surface tension

Bond Strength

metallic

⬇

ionic & covalent

⬇

hydrogen

⬇

dipole-dipole

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LDF