Ch.5:Chemical Bonding: Lewis Structures and Molecular Shapes

Lewis Theory

Explains how atoms bond to form molecules.

Chemical Bond

Forms when bonded atoms' potential energy decreases.

Polar Covalent Bond

Unequal sharing of electrons between unlike atoms.

Electronegativity

Ability of an atom to attract electrons in a bond.

Electronegativity Trend

Increases left to right, decreases top to bottom.

Bond Polarity

Determined by the difference in electronegativity.

Dipole Moment

Measure of charge separation in polar bonds.

Percent Ionic Character

Percentage of bond's dipole compared to ionic bond.

Lewis Structure

Diagram showing bonding and arrangement of valence electrons.

Octet Rule

Atoms are most stable with eight valence electrons.

Central Atom

Least electronegative atom in a molecule.

Formal Charge

Charge assigned to an atom in a molecule.

Resonance Structures

Different ways to represent a molecule's electron distribution.

Bond Energy

Energy required to break a bond between atoms.

Bond Length

Distance between the nuclei of two bonded atoms.

Bond Strength

Energy needed to break a bond; related to bond length.

VSEPR Theory

Predicts molecular shapes based on electron repulsion.

Valence Electrons

Electrons in the outermost shell of an atom.

Anion

Negatively charged ion, gains electrons.

Cation

Positively charged ion, loses electrons.

Single Bond

One pair of electrons shared between two atoms.

Electron Deficiency

Condition where an atom has fewer electrons than needed.

Resonance

Delocalization of electrons across multiple structures.

Octet Rule

Atoms form bonds to achieve eight electrons.

Lewis Structure

Diagram showing electron arrangement in molecules.

Central Atom

Atom bonded to multiple other atoms.

Formal Charge

Charge if bonding electrons shared equally.

Expanded Octet

More than eight electrons around an atom.

Resonance Structures

Different Lewis structures for the same molecule.

Resonance Hybrid

Average of multiple resonance structures.

Bond Strength

Measured by bond enthalpy; energy to break bond.

Bond Length

Distance between nuclei of bonded atoms.

VSEPR Theory

Predicts molecular shape based on electron repulsion.

Bond Enthalpy

Energy required to break a chemical bond.

Single Bond

One pair of electrons shared between atoms.

Double Bond

Two pairs of electrons shared between atoms.

Triple Bond

Three pairs of electrons shared between atoms.

Electronegativity

Tendency of an atom to attract electrons.

Lone Pairs

Non-bonding pairs of electrons on an atom.

Connectivity

Arrangement of atoms in a molecule.

Molecule with Odd Electrons

Example: Nitric Oxide (NO) with unpaired electron.

Formal Charge Calculation

Valence electrons minus lone pairs and half bonding.

Charge Distribution

Preferred structures have fewer and smaller formal charges.

Bond Length Trends

Shorter bonds are generally stronger.

Molecular Shape

Determined by bond angles and electron pairs.

Electron Groups

Valence electron pairs around central atom.

Steric Number (SN)

Total number of electron groups on central atom.

Lone Pair

Non-bonding electron pair on central atom.

Bonding Pair

Electron pair shared between atoms in a bond.

Trigonal Planar Geometry

Three electron groups form a flat triangular shape.

Bent Molecular Geometry

Shape resulting from lone pairs in three groups.

T-shaped Molecular Geometry

Shape with three lone pairs and five groups.

Linear Molecular Geometry

Shape with four lone pairs and five groups.

Square Pyramidal Shape

Shape with one lone pair and six groups.

Square Planar Shape

Shape with two lone pairs and six groups.

Bond Angle

Angle between adjacent bonds in a molecule.

Polarity of Molecules

Molecule's asymmetrical shape and bond dipoles.

Electronegativity Difference

Measure of atom's ability to attract electrons.

Dipole Moment

Vector quantity representing bond polarity.

Vector Addition

Combining multiple dipole moments geometrically.

Polar Molecule

Molecule with net dipole moment due to shape.

Nonpolar Molecule

Molecule with symmetrical shape, dipoles cancel.

VSEPR Model

Predicts molecular shapes based on electron repulsion.

Glycine

Example of a molecule with multiple central atoms.

HCl Bond Polarity

H-Cl bond is polar due to electronegativity.

CO2 Nonpolarity

CO2 is nonpolar due to symmetrical shape.

Water Polarity

Water is polar due to bent shape and lone pairs.