Ions, Cations and Moles, Oh My!

Simple ions:

There is a chart on page 161 of the text. Please consult it. Students will be responsible for knowing all of those ions. Here are some clues, followed by the ions that are on the list:
All positively charged ions (cations) come from metals and are named directly from the element name plus the word "ion", ie hydrogen ion.

all group IA elements form +1 ions: H⁺,Li⁺,Na⁺,K⁺
all group 2A elements form +2 ions: Mg⁺², Ca⁺²

Some metals can have several differently charged ions, so the name of each ion must be specific:

Iron(II) = Fe⁺², Iron (III) = Fe⁺³
Copper (I)= Cu⁺¹, Copper (II) = Cu⁺²

All negatively charged ions are named by adding "ide" to the end after chopping off part (the amount that is chopped off varies, according to what sounds good) of the end of the element name:

all group VIIA elements form -1 charges: Cl^-, Br^-, F^-, I^-
group VI elements tend to form -2 ions: S^-2, O^-2,
group V elements tend to form -3 ions: N^-3

Making compounds with simple ions (binary compounds)

The book uses the cross-over method, and this method is highly successful for most people. So refer to the book for an explanation of that method. Here is another way to approach these problems. Please look at the picture for calcium chloride.

Polyatomic ions

Polyatomic ions contain more than one type of atom. Table 6.2 on page 166 of the text lists many common polyatomic ions. You should know the names, formulas and charges for these ions:

ammonium
bicarbonate
acetate
nitrite
nitrate
cyanide
hydroxide
carbonate
sulfate
phosphate

Here are the ionic compounds potassium phosphate and calcium phosphate.

Naming covalent compounds

The prefixes: mono, di, tri, tetra, penta, hexa, hepta, octa, nano and deca are used to name covalent compounds.

You should know the names and structures for these covalent compounds:

Molar mass calculations

The molar mass for every element is located on your periodic table, under the symbol for each element. These molar masses mean that there are 12 grams per mole of carbon. These molar masses are used to find the molar masses of molecules.

The molar mass of carbon dioxide is

C: 1x12=12
O: 1x16=16
(12+16)=28 g CO per mole of CO.

The molar mass of Potassium phosphate is

K: 3x39=117
P:1x31=31
O:4x16=64
(117+31+64)=212 g K₃PO₄ per mole of K₃PO₄.

Balancing equations

This analogous to balancing your check book: what goes in has to come out! Only it is so much easier to balance reactions than it is to balance a checkbook. Here is the combustion of pentane reaction.

Using balanced equations to determine how much product is formed.

Here is the combustion of hydrogen reaction.

Here are some practice questions:

1. What is the name of NaNO₃?
2. What is the formula of sodium carbonate?
3. How many oxygen atoms are present in nitrous oxide?
4. How many oxygen atoms are present in iron(III) oxide?
5. What is the formula for sodium acetate?
6. What is the molar mass of sodium acetate?
7. How many grams of water can be formed from combusting 10 grams of pentane? Here is the balanced equation for this reaction.
8. How many molecules are in a mole?
9. How many atoms are in a mole?

Koni Stone
Koni@chem.csustan.edu

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