positive two to balance out the two hydroxide anions. Thus, the name of the first
compound is iron (II) hydroxide. The second compound, with three hydroxide
ions, requires an iron cation with a charge of positive three, yielding a name of
iron (III) hydroxide.
A compound like Ti 2 (CO 3 ) 3 is a bit harder to figure out, but it still can be done
by keeping the rule in mind that the entire compound must have a charge of zero.
Each carbonate ion has a charge of negative two, and with three of them, there is
a total charge of negative six. There are two titanium ions present, and each of
those must carry a charge of positive three in order to have a total charge of
positive six to balance the compound. The name of the compound is titanium
(III) carbonate.
The Covalent Bond
When two nonmetals bond, the result is a covalent bond. In a covalent bond, two
atoms share electrons. By sharing electrons, each atom can achieve a stable
octet. In fact, atoms form covalent bonds simply because it’s a way for them to
obtain a stable octet.
Lewis Diagrams
The easiest way to determine how the electrons are shared in a covalent
molecule is to draw a Lewis diagram (also called an electron dot diagram) for
the molecule. To draw a Lewis diagram, use the following steps:
1) Count the number of valence electrons in each atom and add them up.
2) Draw a skeletal structure of the molecule with the least electronegative
atom in the center.
3) Create a single bond (shared electron pair) connecting the central atom
to each terminal atom.
4) Add lone pairs around each terminal and central atom until each atom
has eight total electrons (except hydrogen, which only needs two).
5) Count up the total number of electrons in the structure. If they equal the
total number of valence electrons available (calculated in step 1), your
structure is correct. If you have more assigned electrons than valence
electrons, you need to shift some lone pairs over and create double or triple
bonds.