The Covalent Bonding Model Lecture Notes

A set of vocabulary flashcards covering the Covalent Bonding Model, Lewis structures, octet rules, exceptions, and molecular geometry based on the lecture notes.

Lewis structure

A representation that shows the valence electrons for an atom.

Valence electrons

The electrons that occupy the outermost energy level of an atom and are responsible for the electron activity that occurs to form chemical bonds.

The Octet Rule

The principle that, with the exception of hydrogen & helium, atoms tend to form a structure consisting of eight electrons in the outermost energy level.

Covalent bond

A chemical bond that consists of a pair of electrons shared between two atoms; it is the predominant bond in millions of chemical compounds.

Single bond

A covalent bond formed by $1$ pair of electrons shared between two atoms.

Double bond

A covalent bond formed by $2$ pairs of electrons shared between two atoms.

Triple bond

A covalent bond formed by $3$ pairs of electrons shared between two atoms.

Central atom

In simple molecules with more than two atoms, the atom surrounded by other atoms, usually chosen as the “leftist or lowest” element.

Expanded valence shell

An exception to the Octet Rule where any central atom with outermost electrons in period $3$ or below uses available d orbitals for bonding and can hold $10$ or $12$ electrons.

Electron deficient or free radical structures

Molecules that have less than $8$ electrons and are very reactive compounds due to odd electrons.

Resonance

The movement of electrons within a molecule that serves to stabilize the structure.

Polyatomic ion

A stable group of atoms that has either a positive or negative charge and behaves as a single unit in many chemical reactions.

Electronegativity

The relative attraction that an atom has for a pair of shared electrons in a covalent bond.

Nonpolar covalent bonding

A type of covalent bond where there is equal sharing of electrons, occurring when the two atoms are identical or the electronegativity difference is $0.5$ or less.

Polar covalent bonding

A type of covalent bond where there is unequal sharing of electrons, occurring when the electronegativity difference is less than $1.9$ but greater than $0.5$.

Formal Charge (FC)

A value calculated by the formula: # of valence electrons – (# of electrons + # of bonds).

Ionic bond

A bond formed if the electronegativity difference between two atoms is greater than $1.9$ to $2.0$; if the difference is greater than $2$, the bond is strongly ionic.

V-shaped

The molecular geometry characteristic of water ($H_2O$).

Linear shape

The molecular geometry characteristic of carbon dioxide ($CO_2$).

Trigonal planar

The molecular geometry characteristic of boron trifluoride ($BF_3$).

Tetrahedral

The molecular geometry characteristic of methane ($CH_4$).