Skill 1.3b-Draw Lewis dot structures for compounds and ions

Skill 1.3b-Draw Lewis dot structures for compounds and ions 

Lewis dot structures are a method for keeping track of each atom s valence electrons in a molecule. Drawing Lewis structures is a three-step process  

1) Add the number of valence shell electrons for each atom. See Skill 1.1b for using the periodic table to do this. If the compound is an anion, add the charge of the ion to the total electron count because anions have extra electrons. If the compound is a cation, subtract the charge of the ion. 

2) Write the symbols for each atom showing how the atoms connect to each other. 

3) Draw a single bond (one pair of electron dots or a line) between each pair of connected atoms. Place the remaining electrons around the atoms as unshared pairs. If every atom has an octet of electrons except H atoms with two electrons, the Lewis structure is complete. Shared electrons count towards both atoms. If there are too few electron pairs to do this, draw multiple bonds (two or three pairs of electron dots between the atoms) until an octet is around each atom (except H atoms with two). If there are two many electron pairs to complete the octets with single bonds then the octet rule Is broken for this compound. 

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