Untitled - Kelly Walsh High School

134 CHEMISTRY FOR THE UTTERLY CONFUSED
Quick Tip
Quick Tip
Quick Tip
First, write a general framework for the molecule. In this case, the carbon bonds
to the oxygen since hydrogen can only form one bond.
Hydrogen is never the central atom.
Normally the atom needing the greater number of electrons to achieve an octet
is the central atom. If two atoms need the same number of electrons, the larger
is usually the central atom.
Carbon usually forms four bonds, hydrogen forms one bond, and oxygen generally
forms two bonds.
In order to determine where to place the electrons, we will apply the N-A S
rule
where
H
H C O H
H
N sum of valence electrons needed for each atom. The two allowed
values are 2 for hydrogen and 8 for all other elements.
A sum of all available valence electrons
S no. of electrons shared and S/2 no. of bonds