1-18
Chemistry 121, Winter 2008, LA Tech
Drawing Lewis structure molecules and ions
 (Review)
1) Predict arrangement of atoms.
a)H is always a terminal atom.
b)Halogens and oxygen are often terminal.
c)The central atom of binary compounds is usually written
d)first and has the lowest subscript.
e)Most organic compounds have more than two central atoms.
f)These are mainly C, but N, O and S can also be central atoms.
2) Total number of valence electrons (e-)
a)Add all valence electron of atoms in the molecule from the formula. 
b)Add the ion charge for negative ions or subtract for positive ions.
•