Write the Lewis dot structures of the following molecules or...

Write the Lewis dot structures of the following molecules or ions:
a. HCN;
b. $\mathrm{SO}_3^{2-}$
c. $\mathrm{NO}_2{ }^{+}$;
d. $\mathrm{XeF}_4$;
e. $\mathrm{H}_2 \mathrm{~N}-\mathrm{NH}_2$;
f. $\mathrm{SiH}_4$;
g. $\mathrm{ICl}_4^{-}$.

Key Concepts

Lewis Dot Structure

A Lewis dot structure is a diagrammatic method for showing the bonding between atoms of a molecule and the lone pairs of electrons that may exist. It represents the valence electrons as dots around the symbols of the elements, assisting in visualizing molecular geometry, electron sharing, and the structure of molecules and ions.

Octet Rule

The octet rule is a chemical guideline that atoms tend to form bonds such that each atom has eight electrons in its valence shell, mimicking the electron configuration of a noble gas. This rule is central to determining the arrangement of electrons in Lewis structures, especially for main group elements.

Formal Charge

Formal charge is a bookkeeping tool used in Lewis structures to identify the most stable electron configuration in a molecule or ion. It is calculated by assuming equal sharing of electrons in a bond and comparing the number of electrons around an atom in the Lewis structure to the number it would normally possess, helping to distinguish between alternative structures.

Resonance Structures

Resonance structures are different valid Lewis dot representations of the same molecule or ion that cannot be adequately described by a single structure. They indicate the delocalization of electrons within a molecule, where the true electronic structure is a hybrid of multiple contributing structures.

Expanded Octet

An expanded octet refers to the ability of atoms in period three or beyond to accommodate more than eight electrons in their valence shell. This concept is important when drawing Lewis structures for molecules or ions containing elements such as sulfur, phosphorus, or xenon, where available d-orbitals allow more than four electron pairs to surround an atom.

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