Chemistry 121
Worksheet 3 Notes
Oregon State University
Dr. Richard L Nafshun
1.
Which of the following sets of elements will form a molecular compound? Explain.
(a)
Ni and Cu. No. These are two metals.
(b)
Li and F. No. One metal and one non-metal.
(c)
Li and Mg. No. These are two metals.
(d)
C and Cl. Yes. These are two non-metals.
(e)
He and Mg. No. He does not form compounds—it is an inert gas.
2.
List a pair of elements that will form a molecular compound.
Any two non-metals—for example N and O.
3.
Which of the following substances is an ionic compound? Explain.
(a)
(b)
(c)
(d)
(e)
4.
Octane. No, octane is C8H18, it is a molecule (two non-metals).
Carbon dioxide. No, CO2 is a molecule (two non-metals).
Sodium fluoride. Yes., NaF is an ionic compound (metal and non-metal).
Dinitrogen pentoxide. No, N2O5 is a molecule (two non-metals).
Acetic acid. No, CH3COOH is a molecule (three non-metals).
List a pair of elements that will form an ionic compound.
Any metal and non-metal—for example Al and O (Al2O3). Or, you can use polyatomic
ions (Li2SO4 or NH4NO3).
5.
How many bonds does carbon form? 4. Carbon is in Group 14. It is four groups away
from the inert gases (Group 18).
How many bonds does nitrogen form? 3. Nitrogen is in Group 15. It is three groups
away from the inert gases (Group 18).
How many bonds does oxygen form? 2. Oxygen is in Group 16. It is two groups away
from the inert gases (Group 18).
How many bonds does fluorine form? 1. Fluorine is in Group 17. It is one group
away from the inert gases (Group 18).
How many bonds does argon form? Zero. Argon is in Group 18. It is an inert gas
(Group 18). Consider the Group 18 gases: He has not been shown to make compounds.
It is said that argon has been shown to make compounds, but they are not stable and do
not exist long. The heavier Group 18 gases have actually been shown to make stable
compounds, but this is not easy chemistry.
6.
Sketch a molecule that contains two carbon atoms and six hydrogen atoms.
Name this molecule. Ethane.
What is the chemical formula of this molecule? C2H6.
7.
Sketch a molecule that contains two nitrogen atoms and four hydrogen atoms.
What is the chemical formula of this molecule? Hydrazine. Hydrazine is a colorless
oily liquid that fumes in air.
8.
Sketch a molecule that contains a carbon atom, three chlorine atoms, and a fluorine
atom.
9.
Sketch a molecule that contains two nitrogen atoms.
N≡N
Sketch a molecule that contains two oxygen atoms.
O=O
Sketch a molecule that contains two chlorine atoms.
Cl-Cl
10.
Sketch pentane.
What is the chemical formula of pentane? C5H12.
11.
Sketch octane.
What is the chemical formula of octane? C8H18.
12.
The chemical formula of magnesium phosphate is Mg3(PO4)2.
Is this an ionic or molecular compound? Ionic; magnesium phosphate is a metal and a
polyatomic anion (a group of atoms with a negative charge).
13.
The chemical formula of phosphorous pentachloride is PCl5.
Is this an ionic or molecular compound? Molecular compound; a non-metal (P) and a
non-metal (Cl).