Lewis Dot Symbols: Represent valence electrons of atoms/ions. Main group elements: valence electrons = group number; transition metals: variable valence electrons.

Drawing Lewis Dot Symbols: Place one valence electron on each side of the element symbol, then pair up as needed. For ions, add or remove electrons accordingly.

Ionic Bonding: Involves transfer of electrons from metals (which lose electrons) to nonmetals (which gain electrons), forming cations and anions. Ionic bonds lower the energy of the system.

Covalent Bonding: Involves sharing of valence electrons between nonmetals. Atoms achieve stable octets by sharing electrons.

Metallic Bonding: Involves free-flowing valence electrons among a lattice of metal ions, giving rise to properties like conductivity, malleability, and luster.

Electronegativity (EN): Measures an atom's ability to attract electrons. EN increases across a period and up a group. ΔEN = EN2 - EN1

Dipole Moment: Arises from differences in electronegativity between bonded atoms, creating partial charges and molecular polarity.

Chemical Bond Classifications:

• Nonpolar covalent: 0.0 EN difference

• Polar covalent: 0.1 - 1.7 EN difference

• Ionic: >1.7 EN difference

Octet Rule: Main group elements tend to achieve 8 valence electrons.

• Incomplete octet: Fewer than 8 electrons (e.g., Be, B)

• Expanded octet: More than 8 electrons (elements in period 3 and below)

Formal Charge: Used to determine the most stable Lewis structure. Formal Charge = Valence Electrons - (Nonbonding Electrons + Bonding Electrons2)

Best Lewis Structure: Minimizes formal charges and places negative charges on more electronegative atoms.

Lone Pairs: Nonbonding pairs of electrons on an atom, not involved in bonding.

Sigma (σ) and Pi (π) Bonds:

• Sigma: First bond between two atoms, strongest type.

• Pi: Additional bonds in double/triple bonds, weaker than sigma.

Bond Strength and Length: Greater bond strength = shorter bond length. Triple bonds are stronger and shorter than double or single bonds.

Lewis Structures for Ions and Ionic Compounds: Draw ions separately, showing their charges, and arrange to reflect electrostatic attraction.

Radicals: Molecules or ions with an unpaired electron. Place the unpaired electron on the atom with the lowest formal charge.