Chapter 6 Notes – The Structure of Matter

Section 6.1 – Compounds and Molecules

A compound is made of two or more elements that are chemically combined. The forces that hold atoms or ions together in a compound are called chemical bonds.

Chemical Structure

Water’s chemical formula tells us what atoms make up water, but it does not tell us anything about the way the atoms are connected.

A compound’s chemical structure is the way the compound’s atoms are bonded to make the compound.

Section 6.2 – Ionic and Covalent Bonds

Atoms bond when their valence electrons interact. Generally, atoms join to form bonds so that each atom has a stable electron configuration.

There are two basic kinds of chemical bonding: ionic bonding and covalent bonding. Draw Figure 1 – Comparing Ionic and Covalent Compounds in the space provided below to show the various properties of ionic vs. covalent bonds.

Ionic bonds form from the attraction between oppositely charged ions.

-Some atoms form bonds because they transfer electrons. One of the atoms gains the electrons that the other one loses. Draw the picture on page 184 to show how an atom of sodium and chlorine form an ionic bond.

-When melted or dissolved in water, ionic compounds conduct electricity.

-Electric current is moving charges. Solid NaCl does not conduct electricity because the ions are locked in place. If you dissolve NaCl in water, the ions move around and an electric current is able to move through it.

-Covalent bonds are atoms that share electrons and are made up of molecules. Covalent bonds usually occur between nonmetal atoms.

-Most covalent bonds do not conduct electricity because they are sharing electrons. Therefore, they do not have a charge.

-Before bonding, chlorine has 7 valence electrons. When 2 chlorine atoms bond, they share one electrons with one another and have a full outermost shell.

-A single line between two atoms represents that two electrons are being shared.

-Two lines between two atoms represent four electrons being shared.

-Three lines between two atoms represent six electrons being shared.

-More energy is needed to break apart a triple bond than a double or single bond.

When electrons are shared equally between the same atoms, they are called nonpolarcovalent bonds.

When two atoms of different elements share electrons, the electrons are not shared equally and they are known as polar covalent bonds.

Usually, electrons are more attracted to atoms of elements that are located farther to the right and closer to the top of the periodic table.

Metallic Bonds

Metals are flexible and conduct electric current well because their atoms and electrons can move freely throughout a metal’s packed structure.

Polyatomic Ions

Some compounds have both ionic and covalent bonds. Such compounds are made of polyatomic ions, which are groups of covalently bonded atoms that have a positive or negative charge as a group.

A polyatomic ion acts as a single unit in a compound, just as ions that consist of a single atom do.

Common polyatomic ions are baking soda and soap. Baking soda is known as sodium hydrogen carbonate, NaHCO3. Sodium carbonate, Na2CO3, is found in soaps.

-Oppositely charged polyatomic ions can bond to form a compound.

Most polyatomic ions are made of oxygen. Most of their names end with –ite or –ate. An –ate ending is usually used to name an ion that has three oxygen atoms. Names that end it –ite have two or fewer oxygen atoms.

Use page 190 to fill in the following charts.

Some Common Polyatomic Anions

Ion Name / Ion Formula
Acetate ion
Carbonate ion
Chlorate ion
Chlorite ion
Cyanide ion
Hydrogen carbonate ion
Hydrogen sulfate ion
Hydrogen sulfite ion
Ion Name / Ion Formula
Hydroxide ion
Hypochlorite ion
Nitrate ion
Nitrite ion
Phosphate ion
Phosphite ion
Sulfate ion
Sulfite ion

Section 6.3 – Compound Names and Formulas

The names of ionic compounds consist of the names of the ions that make up the compounds.

In many cases, the name of the cation is just like the name of its element. For example, when sodium loses an electron it is stilled called sodium.

An anion of an element has a name similar to that element’s name. The difference is the name’s ending. Draw the chart in the space provided below of Figure 2 on page 192.

Transition metal cations will always be given to you. For example, Copper (I) ion has a C +1 charge. Iron (III) ion has a Fe +3 charge. The number in parentheses is the charge that the metal has.

Follow the rules below to name monoatomic atoms. These rules apply to naming ionic bonds.

  1. Write the name of the 1st element.
  2. Write the root name of the second element.
  3. Add the ending IDE to the root name of the second element.

For example: Chlorine – ine and add ide = Chloride

Let’s Practice!!!

Write the name of the following compound.

BP –

LiF –

MgO –

The following are common polyatomic ions that you will use when naming polyatomic compounds.

Follow these rules to name polyatomic atoms.

  1. Write the name of the 1st element with positive ion.
  2. Write the name of the 2nd element with negative ion.

For example: Mg(CO3)

Mg+2 and CO3-2 = Magnesium Carbonate

Naming Covalent Compounds

For covalent compounds of two elements, numerical prefixes tell how many atoms of each element are in the molecule.

Use Figure 5 on page 194 for the prefixes that you will need.

If there is only one atom of the first element, the name does not get a prefix.

BF3 = Boron trifluoride

N2O4 = Dinitrogen tetraoxide

Try these!!!!

P2S3 =

Cl2O =

NF3 =