VOCABULARY:

Chemical Symbol: A notation using one to three letters to represent an element.

Ion: An atom or molecule that has gained or lost one or more electrons.

Chemical Formula: The notation using symbols and numerals to represent the composition of substances.

Oxidation Number: The apparent charge on an atom if the electrons in a compound are assigned according to established rules.

Polyatomic Ion: A group of atoms covanlently bonded but possessing an overall charge.

Ionic Compound: A compound that is formed by ionic bonds.

Molecule: A neutral group of atoms held together by covalent bonds.

Binary Compound: A compound composed of only two elements.

Molecular Formula: A formula indicating the actual number of atoms of each element making up a molecule.

Empirical Formula: The formula giving the simplest ratio between the atoms of the elements present in the compound.

Formula Unit: The amount of a substance represented by its formula.

OXIDATION NUMBER:

Through experiments, chemists have determined the ___________________ in which most elements combine. They have also learned that these ratios depend on the ___________________ of the atoms of the elements.

When an atom reacts to form an ion, the ___________________ of an octet of electrons enables you to predict the charge on the ion formed.

When a single atom takes on a charge, it is called a ___________________ . The charge on a ___________________ is known as the oxidation number of the atom.

Most of these charges can be verified by applying the octet rule. An ion made of more than one atom, for example, OH^-1, is called a ___________________ ion.

CHEMICAL FORMULAS:

A chemical formula tells you what kinds of ___________________ and how many of each kind are combined together.

A chemical formula consists of the symbols of the elements accompanied by ___________________ to the right of the symbols.

In a compound or molecule, the ___________________ indicates the number of atoms of the element to its ___________________ . For example, the formula H₂ tells you that there are two hydrogen atoms that compose one hydrogen molecule.

The list of formulas are examples of elements that exist in nature as ___________________ molecules.

FORMULAS OF COMPOUNDS:

Every compound is represented by a ___________________ . The formula for water, H₂O, indicates that one molecule of water is made up of two atoms of hydrogen and one atom of oxygen.

___________________ compounds such as salt (sodium chloride) NaCl, exist as extended networks of ions. Since these networks vary in size, the formula indicates the ___________________ whole-number ratio of each element in the compound and is called a formula unit.

For example, CuO and Cu₂O are the chemical formulas for two compounds of copper and oxygen. The first formula indicates that there is ___________________ atom of copper for each atom of oxygen in the ionic network. The second formula shown indicates that there are ___________________ atoms of copper for each atom of oxygen in the ionic network.

RULES FOR WRITING FORMULAS:

The first two rules for writing formulas are:

Rule 1: Represent each kind of element in a compound with the ___________________ for that element.

Rule 2: Use subscripts to indicate the number of atoms of each element in the compound. If there is only one atom of a particular element, ___________________ is used.

Applying these rules for a molecule of one atom of oxygen, O, and two atoms of hydrogen, H, the formula could be written OH₂. To avoid confusion, the symbols are written in a particular order.

Rule 3: Write the symbol for the MORE ___________________ element first.

Neither hydrogen nor oxygen is a metal. However, the location of hydrogen with the metallic elements in the periodic table suggests that is should appear before oxygen in the formula.

Similarly, for a compound containing oxygen and sulfur, the location of sulfur is ___________________ oxygen in the periodic table suggests that it is more metallic than oxygen and should be written first in the formula.

For example, SO₂ is a compound formed when sulfur burns.

Using these three rules, you can write the correct formula for almost any compound if you know the elements it contains and the number of atoms of each element in one molecule (or formula unit) of that compound. However, the only way chemists can get that information is by ___________________ analysis.

Formulas are a convenient way to represent compounds, but compounds have names as well. There are Millions of compounds, so it is IMPOSSIBLE to memorize all their names (or Function).

Learning the rules for naming compounds will help you figure out their names.

Unfortunately many common compounds were named before it became obvious that a systematic method would be needed. H₂O is called water be everyone (including chemists), even though its systematic name is dihydrogen monoxide.

NAMING BINARY MOLECULAR COMPOUNDS: ( NON-METAL with NON-METAL )

The first system is used to name binary compounds that exist as ___________________ molecules rather than as ionic compounds.

Binary compounds are compounds made up of ___________________ elements.

There is ___________________ to look at the formula of a compound and know whether it is molecular or ionic. However, binary compounds containing two nonmetals are ALWAYS molecular, whereas binary compounds containing a metal and a nonmetal are usually ionic.

If you are not sure whether a compound is ionic or molecular, look to see if it contains a ___________________ . If it does not, use the following system to name it.

The name tells what elements are in the molecule and includes Greek prefixes to indicate the number of atoms of each element present. The system involves these steps:

1. Name the elements in the ___________________ that they appear in the formula.

2. Drop the last ___________________ (two syllables in some cases) in the name of the final element and add -ide.

3. Add ___________________ to the name of each element to indicate the number of atoms of that element in the molecule.

* * * In practice, the mono- prefix is omitted for the first element in the name.

Below describes the steps that are used to name CO₂. Notice how each step in the naming process reduces ambiguity about what compound is being named.

The first step clarifies what elements are involved, but the resulting name does not make clear that the elements are in a compound.

Changing the ending of the second element, in step two, signals that you are talking about a ___________________ rather than isolated elements.

Step three adds prefixes to indicate the number of atoms of each element present.

Example: What is the name of the compound N₂O₄?

Practice Problems: Name the following compounds.

SiC

CS₂

SF₆

SiO₂

B₂O₃

N₂O₅

Write the formula of the following compounds.

chlorine dioxide

dichlorine monoxide

diphosphorus tetroxide

tetrasulfur dinitride

iodine heptafluoride

tetraarsenic decoxide

HOMEWORK - NAMING COMPOUNDS - PART I: (BINARY COMPOUNDS)

FORMULAS AND NAMES OF IONIC COMPOUNDS: (METAL with NON-METAL)

The smallest unit of molecular compound capable of ___________________ the chemical characteristics of the compound is a molecule.

In ionic compounds, however, because ions exist in an extended network, there is no single unit. Consequently using Greek prefixes (which you will use to name Molecular Compounds) to indicate the number of atoms in a molecule of the compound is not used.

Ionic compounds can form from ___________________ and ___________________ . The metallic elements in these compounds have a positive (+) charge and the nonmetallic elements have a negative (-) charge.

It is necessary to know the ___________________ on each ion for determining the formula and to name ionic compounds.

USING ION CHARGE TO PREDICT FORMULAS:

Before you can write the formulas for ionic compounds, you must remember how to predict the ___________________ on ions. Fortunately, the charge on many ions can be predicted from the periodic table, and the charge on other ions can be calculated.

Predicting ion charge from the periodic table:

The following rules for finding the charge on an ion are based on regularities discovered by analyzing ionic compounds.

Rule 1: Ions formed from elements in the Alkali ion group have a +1 charge.

Rule 2: Ions formed from elements in the Alkali Earth ion group have a +2 charge.

Rule 3: Aluminum ions have a +3 charge. Other elements in this group normally form ions with a +3 charge, but there are exceptions.

Rule 4: Elements in all other groups form ions with various charges.

a. Non-metals that are in the group (column) as Nitrogen will have a -3 charge.

b. Non-metals that are in the group (column) as Oxygen will have a -2 charge.

c. All halogens form halide ions with a -1 charge. (Halides are binary compounds of a metal and a halogen).

Rule 5: The ALGEBRAIC SUM of the charges in a compound is zero ( unless otherwise stated - we will discuss this very soon).

Example: Predict the formula for a compound of calcium and chlorine.

Practice Problems:

Write the formula for the ionic compounds of the elements listed.

magnesium and oxygen

aluminum and bromine

sodium and sulfur

oxygen and aluminum

potassium and nitrogen

bromine and cesium

potassium and iodide

oxygen and magnesium

The formulas for ionic compounds such as those in the problems above look just like the formulas for molecular compounds, such as CO₂.

However, there is an important difference in ionic and molecular compounds that does not show in the formulas. Ions that compose ionic compounds can ___________________ or separate from the ionic network (which we will discuss in more detail next semester).

For example, calcium chloride dissolves in water, the compound comes apart (dissociates) to form separate calcium ions and chloride ions. These ions are represented by Ca⁺² and Cl^-1

Example: What is the formula name for CaO?

Practice Problems:

Use the periodic table to predict the formula names for these ionic compounds.

KBr

Cs₂O

Mg₃N₂

BaBr₂

Na₃N

Sr₃N₂

K₃P

LiF

HOMEWORK - NAMING COMPOUNDS - PART II: (IONIC COMPOUNDS)

PREDICTING FORMULAS CONTAINING POLYATOMIC IONS:

Vinegar is a water solution of a compound with formula HC₂H₃O₂. Vinegar conducts an electric current so you know that it must contain ions. Experiments show that one of the ions is H⁺¹. The other is C₂H₃O₂^-1, which is composed of several atoms joined together with a -1 charge on the ion as a whole. Such ions are called ___________________ ions.

Sulfuric acid, the substance added to water to increase its conductivity in an electrolysis experiment, has the formula H₂SO₄. It breaks apart in water to give H⁺¹ and HSO₄^-1, another polyatomic ion with a -1 charge. Under certain conditions, this HSO₄^-1 ion breaks apart to form H⁺¹ and SO₄^-2.

It is difficult to predict what compounds will break apart into ions or what ions they will form until you have learned more about chemistry.

The formulas for compounds containing polyatomic ions are predicted in exactly the same ways that you predicted formulas for other compounds containing ions.

The positive (metallic) ion is written first, followed by the negative ion. Remember that the algebraic sum of the charges must be zero.

The only thing new is that the charge on the polyatomic ion pertains to the ion as a whole before a subscript is written.

Also, a few things to help you recognize a polyatomic ion is in the formula:

- if name ends in -ate, or -ite (ALWAYS polyatomic), an -ide ending USUALLY means the non-metal is monoatomic (example: hydroxide, amide, peroxide)

- if you have more than TWO different types of elements present = polyatomic

- to find where the polyatomic ion is located do a few checks: ( Example: NaC₂H₃O₂ and NH₄NO₃ )

1. identify the metal: Once you have identified the metal what ever remains is the non-metal.

2. if a non-metal starts the formula you may have a positive polyatomic ion.

Example: What is the formula for a compound containing calcium ions and hydroxide ions?

Practice Problems:

Write the formula for the following compounds.

calcium acetate

sodium phosphate

hydroxide ions and aluminum ions

ammonium phosphate

potassium nitrate

calcium ions and carbonate ions

NAMING IONIC COMPOUNDS:

You have learned to name molecular compounds. The common system for naming ionic compounds is a little different because Greek prefixes are ___________________ . If the compound is composed of ions - simply name the ions of the compound.

The name of the negative ion in binary compounds always end in -ide, just as the name of binary molecular compounds end in -ide.

If the compound contains a polyatomic ion, use the name of the ion as it is written on the polyatomic ion sheet. Use the polyatomic ion sheet and the periodic table as guides in assigning names to ionic compounds.

Example: What is the name of (NH₄)₂SO₄?

Practice Problems:

Name these ionic compounds.

Na₂O

Mg(OH)₂

Al(NO₃)₃

NH₄Cl

HOMEWORK - NAMING COMPOUNDS - PART III (POLYATOMIC IONS)

PREDICTING ION CHARGE FROM A CHEMICAL FORMULA:

So far you have seen how to name compounds containing polyatomic ions and elements whose charges can be predicted. However, there are many elements that form ___________________ ionic compound, and the charge on the metal ion varies form one compound to another.

For example, iron and chloride form two ionic compounds, FeCl₂ and FeCl₃. If both compounds were called iron chloride, you would not know which compound was meant.

The name must indicate which compound is described. Ionic compounds are named by indicating the charge on the METAL ion by a Roman numeral.

Therefore FeCl₂ is iron(II)chloride and FeCl₃ is iron(III)chloride. There is no space between the name of the metal and the parentheses indicating the charge on the ion.

Also, keep in mind that the Roman numeral does NOT indicate the number of atoms of an element in the formula.

For example, FeO is the formula for iron(II)oxide. The formula indicates a ratio of one iron ion to one oxide ion. The Roman numeral (II) indicates that the charge on the metal (iron) ion is +2.

Example: How would you name the ionic compound CoCl₂?

Practice Problems: Names the following ionic compounds.

Sn(NO₃)₂

Cu₂CO₃

NiC₂O₄

Cr₂O₃

HOMEWORK - NAMING COMPOUNDS - PART IV (IONIC COMPOUNDS II)

NAMING ACIDS:

When dissolved in water, certain molecules produce H⁺¹ ions (protons). These substances, which are called acids, were first recognized by the sour taste of their solutions. For example, citric acid is responsible for the tartness of lemons and limes. Acids will be discussed in detail later next semester. Here we are simply learning how to name acids (using the correct rules).

An acid can be viewed as a molecule with one or more H⁺¹ ions attached to an anion. These rules for naming acids depends on whether the anion contains oxygen.

ANION DOES NOT CONTAIN OXYGEN:

If the anion does not contain oxygen, the acid is named with the prefix hydro- and the suffix -ic attached to the root name of the element. For example, when gaseous HCl (hydrogen chloride) is dissolved in water, it forms hydrochloric acid.

Practice Problems:

HCN

H₂S

ANION DOES CONTAIN OXYGEN:

When the anion contains oxygen, the acid name is formed from the root name of the central element of the anion or the anion name, with a suffix of -ic or -ous.

When the anion name ends in -ate, the suffix -ic is used.

Example:

Acid	Anion	Name
H2SO4	SO4 -2 (sulfate)	sulfuric acid
HNO3	NO3 -1 (nitrate)	nitric acid
HC2H3O2	C2H3O2 -1 (acetate)	acetic acid

When the anion name ends in -ite, the suffix -ous is used.

Example:

Acid	Anion	Name
H2SO3	SO3 -2 (sulfite)	sulfurous acid
HNO2	NO2 -1 (nitrite)	nitrous acid

Practice Problems:

H₃PO₄

H₂CO₃

HI

HIO₂

H₃C₆H₈O₇

HClO₄

HF

H₃P

HC₃H₅O₃