CH 115 Fall 2015
Worksheet 7
1. How do you distinguish an ionic compound from a covalent compound?
Ionic – metal and nonmetal, NOT sharing electrons
Covalent/molecular – nonmetal and nonmetal, sharing electrons to form a bond
The first step to naming a compound is to decide whether that compound is ionic or
covalent, so make sure you can distinguish between the two!
2. What are some rules for naming cations? Anions? Ionic compounds? (Think about how
these rules differ from naming covalent compounds).
Cations – name is same as name on periodic table
Anions – name on the periodic table + suffix of “ide”
Ionic compounds – name of cation comes first, name of anion comes second
Remember we don’t include Greek number prefixes for ionic compounds!
Transition metals – include roman numeral indicating charge in parentheses
3. What is a polyatomic ion? Where can you find a list of the polyatomic ions that you
should memorize for the test?
Charged species with multiple atoms bonded together with covalent bonds - but will
make ionic bonds with another ion!
List is Table 2.2 in your book (or just google search) – pg. 58.
MEMORIZE THIS LIST. YOU WILL NEED IT FOR THE REST OF THE
SEMESTER AND NEXT SEMESTER!
There are a few patterns that might help you memorize, although using flashcards is
probably the best way to go about it. Notice the endings of the names of the ions and
the number of oxygens in the polyatomic ion (e.g. chlorite and nitrite both end in ite
and have 2 oxygen atoms)
4. Fill in the table below.
Phosphorus trichloride
Sodium nitride
Aluminum phosphate
Acetate ion
PCl3
Na3N
AlPO4
CH3COO-
Perchlorate
Calcium dichromate
Carbonate ion
Copper (II) Sulfate
ClO4CaCr2O7
CO32CuSO4
5. Write the name/formula for the following compounds and indicate whether they are ionic
or covalent.
a). Sodium sulfate – ionic, Na2SO4
b). K2Cr2O7 – ionic, potassium dichromate
c). Iron (III) permanganate – ionic, Fe(MnO4)3
d). NH3 – covalent, ammonia
e). Sulfur hexafluoride – covalent, SF6
f). Calcium phosphate – ionic, Ca3(PO4)2
CH 115 Fall 2015
Worksheet 7
g). Aluminum carbonate – ionic, Al2(CO3)3
h). NaClO3 – ionic, sodium chlorate
i). Cl2O – covalent, dichloride monoxide
j). Ammonium hydroxide – ionic, NH4OH
k). BCl3 – covalent, boron trichloride
6. What does VSEPR stand for and what does it mean? What dictates the geometry of a
particular compound?
Valence shell electron pair repulsion theory – means that the repulsion occurring
between the valence electron pairs on the central atom are causing what molecular
and electronic geometries that we can observe.
7. What is the difference between the electronic (electron-pair) geometry and the molecular
geometry of a compound? Can these two geometries ever be the same for a particular
compound? Given the formula of a compound, describe how you would determine its
electronic and molecular geometries.
Electronic geometry is dictated by all of the regions of electron density around the
central atom. Molecular geometry is the actual shape of the molecule and takes into
account the lone pairs that are present around the central atom. These two
geometries can be the same if there are no lone pairs around the central atom.
LOOK IN YOUR BOOK FOR A TABLE OF ELECTRONIC AND MOLECULAR
GEOMETRIES AND BOND ANGLES THAT YOU WILL NEED TO HAVE
MEMORIZED FOR THE TEST.
To find geometries:
1. Draw the Lewis structure!
2. Count the regions of electron density that surround the central atom (remember
lone pairs count as one, as do double and triple bonds).
3. Decide the electronic geometry based on the number of regions counted.
4. Count the number of lone pairs.
5. Decide the molecular geometry and bond angles based on number of lone pairs.