Knowt 7 - Chemical Bonding & Molecular Geometry

Ionic Bonds

Strong electrostatic force of attraction between cations and anions in an ionic compound.

Covalent Bonds

Bond formed when electrons are shared between atoms.

Pure (Nonpolar) Covalent Bond

Equal Electrostatics share of electrons

Polar Covalent Bond

Unequal electrostatics share of electrons

Electronegativity

Tendency of an atom to attract electrons in a bond to itself.

Lewis Symbol

Illustrates the atoms valence electrons

Lewis Structures

Diagram showing lone pairs and bonding pairs of electrons in a molecule or an ion.

Lone Pairs

Two (a pair of) valence electrons that are not used to form a covalent bond.

Single Bond

Bond in which a single pair of electrons is shared between two atoms.

Double Bond

Covalent bond in which two pairs of electrons are shared between two atoms.

Triple Bond

Bond in which three pairs of electrons are shared between two atoms.

Octet Rule

Fills up all 8 valence electrons

Free Radicals

Molecule that contains an odd number of electrons.

Hypervalent Molecules

Molecule containing at least one main group element that has more than eight electrons in its valence shell.

Formal Charge

A way to calculate the charge on an atom in a Lewis structure.

Resonance

When a molecule's structure is a mix of multiple possible electron arrangements.

Molecular Structure

The 3D arrangement of atoms in a molecule

Bond Length (Distance)

The shortest distance between the centers of two bonded atoms.

Bond Energy

The energy required to break a bond between two atoms in a gas.

Bond Angle

The angle formed by two bonds meeting at a shared atom.

VSEPR Theory

• Valence Shell Electron-Pair Repulsion

• A theory predicting shapes by minimizing electron repulsions.

Linear

A straight-line arrangement with two groups opposite each other.

Trigonal Planar

A flat triangle shape with three groups at 120° angles.

Trigonal Planar - 1 Lone Pair

Bent or Angular

Tetrahedral

A shape with four groups at 109.5° angles around a central atoms

Tetrahedral - 1 Lone Pair

Trigonal Pyramid

Tetrahedral - 2 Lone Pair

Bent or Angular

Trigonal Bipyramid

A shape with five groups: three in a triangle and two above/below.

Trigonal Bipyramid - 1 Lone Pair

Sawhorse or Seesaw

Trigonal Bipyramid - 2 Lone Pair

T-Shape

Trigonal Bipyramid - 3 Lone Pair

Linear

Octahedral

A shape with six groups around a central atom in a 3D square pyramid.

Octahedral - 1 Lone Pair

Square Pyramid

Octahedral - 2 Lone Pair

Square Planar

Octahedral - 3 Lone Pair

T-Shape

Octahedral - 4 Lone Pair

Linear

Electron - Pair Geometry

How electron groups are positioned around a central atom.

Axial Position

A position in trigonal bipyramidal shape at 180° from another.

Equatorial Position

One of three positions in trigonal bipyramidal shape at 120° angles.

Bond Dipole Moment

A measure of charge separation in a bond due to unequal electron sharing.

Vector

A quantity with both magnitude and direction.

Polar Molecule

A molecule with an uneven charge distribution.

Dipole Moment

The net separation of positive and negative charges in a molecule.

Formal Charge Equation

F.C = # valence shell electrons (free atom) - # lone pair electrons - ½ # bonding electrons

Bond Energy for a diatomic molecule - Equation Concept

XY (g) → X(g) + Y (g)

D_X—Y = ∆H°

Enthalpy Change Equation

ΔH = ƩD_{bonds broken} – ƩD_{bonds formed}