Writing Lewis Structures for Covalent Compounds

VOCABULARY flashcards covering the steps and rules for drawing Lewis structures for covalent compounds, including exceptions and advanced concepts like resonance.

Covalent Compounds

Molecules formed when two or more nonmetals bond together by sharing electrons.

Valence Electrons

Outer shell electrons determined by the group number on the periodic table, such as Group 1 having $1$ and Group 18 having $8$ electrons (excluding transition metals).

Carbon Dioxide ($CO_2$) Valence Count

A molecule consisting of one Carbon atom ($4$ valence electrons) and two Oxygen atoms ($6 \times 2$ valence electrons), totaling $16$ valence electrons.

Dinitrogen Monoxide ($N_2O$) Valence Count

A molecule consisting of two Nitrogen atoms ($5 \times 2$ valence electrons) and one Oxygen atom ($6$ valence electrons), totaling $16$ valence electrons.

Methane ($CH_4$) Valence Count

A molecule consisting of one Carbon atom ($4$ valence electrons) and four Hydrogen atoms ($1 \times 4$ valence electrons), totaling $8$ valence electrons.

Least Electronegative Element

The element that is typically placed in the center of a Lewis structure, excluding Hydrogen.

Hydrogen Exception

An element that always goes on the outside of a Lewis structure and only requires $2$ valence electrons to have a full outer shell.

Electronegativity Trend

The tendency of an atom to attract electrons, which increases as you move towards Fluorine on the periodic table.

Octet Rule

The requirement for most atoms in a Lewis structure to be surrounded by $8$ valence electrons to achieve stability.

Double or Triple Bonds

Bonding structures formed by moving electron pairs between atoms when all valence electrons are used but the center atoms do not yet have an octet.

Expanded Octet

A condition occurring in elements from period $3$ and below where an atom can have more than $8$ valence electrons, such as the $10$ electrons in $BrCl_5$.

Resonance

A situation where there are multiple ways to draw a Lewis structure for the same molecule; the actual structure is an average of these possibilities.

Equivalent Resonance Structures

Multiple identical Lewis structures that differ only in the placement of double or triple bonds, which do not actually switch back and forth in real life.

Formal Charges

A conceptual tool used to identify the most likely or favorable Lewis structure when several non-equivalent resonance structures can be drawn.