Important Points about Ionic Compounds
Ionic compounds consist of positively and negatively charged ions. An example
of this type is sodium chloride, NaCl. In this compound a neutral sodium atom transfers
one electron to a neutral chlorine atom. This electron transfer results a sodium ion (Na+1)
and a chlorine atom (Cl-1). The compound NaCl is formed by the attraction between these
two ions. In general, positively charged ions (cations) are mental ions and negatively
charged ions (anions) are nonmetal ions. Consequently, ionic compounds are generally
formed between metals and nonmetals.
Recall: We name ionic compounds by simply writing the name of the metal first,
dropping the last syllable of the non-metal’s name, and adding “ide”.
Example: Name the following:
a) CaCl2 – Calcium chloride
b) Na2SO4 – Sodium sulfate
(metal + non metal)
Important Points about Covalent Compounds:
 Covalent compounds result from sharing electrons between atoms to form
covalent bonds. They result when a non-metal bonds with a non-metal; remember
non-metals are on the right side of the periodic table. – Metallic Stair Case
 Covalent bonds are formed between atoms that have similar properties, or have
similar electronegativities. (See electronegativity table handout; the higher the
electronegativity number the more it wants the electron.)
 Compounds formed from atoms that tend to share electrons equally with each
other are said to be non-polar covalent compounds.
 Compounds formed from atoms that share unequally (electronegativities are
different) Are called polar covalent compounds. The electron pairs are pulled
toward that atom that has the higher electronegativity.
 Polar covalent compounds are “slightly” positive at one end, and “slightly”
negative at another. We show these “slight” charges with a delta symbol.
Ex:
H


O(-)
O δ-
or
H
H
H
When a bond is formed between hydrogen and oxygen, or between carbon and
oxygen, the electrons in the bond are pulled toward the oxygen because it has a
larger electronegativity (want for the electron)
Recall: The naming of covalent molecules is more complex. We use prefixes.
Write the leftmost element first unchanged, followed by the rightmost element
adding the “ide” ending to it like you would in ionic bonding. Finally, we use
prefixes to indicate the number of elements in the molecule.
Prefixes: Mono –1
Ex: H2O
dihydrogen monoxide
***Hydrogen is not a metal here!!!!
Di - 2
Tri - 3
Tetra - 4
Penta - 5
Hexa - 6
Hepta – 7
Octa – 8
Nano – 9
Deca -10
Ex: PCl5
Phosphorus pentacloride
***We don’t need to write mono!