5.3-Compound Names and
Formulas
I can:
-use the period table to determine period charge in Groups 1, 2, and 17,
including hydrogen and oxygen
-identify a compound using conventional naming systems that include Greek
prefixes where appropriate (Prefixes limited to represent values from one to
10)
-identify the formula for a covalent or ionic substance
Naming Ionic Compounds
▪ Formed by cations-anions.
▪ Both ions are included in name.
▪ Naming of cations include the
elements of which they are
composed.
▪ Sodium loses an electron= Na+
▪ Calcium loses two electrons= Ca2+
▪ Aluminum loses three electrons=
Al3+
– Group 1 ions have 1+ charge, while
group 2 has 2+ charge
Naming Ionic Compounds, cont.
▪ Names of anions are altered
names of elements.
– Same group will have same charge
– “ide” is placed as suffix
▪ NaF=sodium fluoride
Same cation names must show their charge
▪ FeO v. Fe2O3
– Both named iron oxide
– See the problem?
▪ Transition metals can form
several cations with different
charges.
▪ Some cation name must be
followed by Roman numeral in
parentheses.
– Fe2O3 = Fe3+, Iron(III) oxide.
– now where did the Fe3+ come
from?
Determining the charge of a transition
metal cation.
▪ Total charge must be 0!
▪ https://www.youtube.com/watch?v=_w6-4fRQt1Y
Writing Formulas for Ionic Compounds
▪ What is the formula for Aluminum Fluoride?
– AlF3
Naming Covalent Compounds
▪ SiO2 (silicon dioxide) and CO2
(Carbon Dioxide)
▪ Where are they on the periodic table?
▪ Numerical (#’s) prefixes are used to
name covalent compounds of two
elements
– Tells how many atoms of each element
– 1 atom in first element does not get
prefix
– Whichever element is further right on
periodic table is named second and ends
in “ide.”
– In other words, start with one that is
more metal like.
▪ BF3
– Boron trifluoride
▪ N204
– Dinitrogen Tetroxide
▪ CO?
Chemical Formulas for Covalent Compounds
▪ Mass of each element in
compounds must be measured
first.
▪ Empirical Formula (simplest):
Tells smallest whole-number
ratio of atoms that are in
compound. (reduced to ratio)
– H2O= 2:1 ratio
– Problem: compounds can have
same empirical formula, but be
very different.
Molecular formulas are determined from
empirical formulas.
▪ Each compound has its own Moleculelar formula: chemical formula
that shows the number and kinds of atoms in a molecule, but not the
arrangement of atoms. (actual number)
▪ Look at examples on previous slide.
practice
▪ http://www.sciencegeek.net/Chemistry/taters/Unit3BinaryNomencla
ture.htm