Chapter 12: Simple Compounds & Chemical Formulas

Front 1

Molecular Formula

Back 1

Tells us the actual number of the different elements in one molecule of a compound

Front 2

Empirical Formula

Back 2

Is defined as the simplest ratio of whole numbers of elements that make up a compound, and this type of formula is derived from experimental data.

Front 3

Structural Formula

Back 3

Shows both the actual number of atoms of elements in a compound, how the atoms are arranged as well as which atoms are bonded to one another

Front 4

Condensed Structural Forumula

Back 4

Shows the position of atoms in relation to one another without showing their bonds.

Front 5

Octet Rule

Back 5

Atoms like to have full outer shells of only eight electrons.

Front 6

Lewis dot structure

Back 6

A quick and easy diagram that shows the valence electrons in an element

Front 7

Back 7

Atoms can gain or lose more than one electron at a time.

If they do, they are written with the superscript of what they have gained or lost.

Ca2+, for instance, has lost two electrons.

Front 8

When Atom Lose/Gain Electrons

Back 8

If they have less than three valence electrons, it is easier to lose them and become a positively charged ion.

If they have more than four valence electrons, it is easier to gain electrons and become negatively charged.

• At four it is +/- split

Front 9

Ionic Compounds

Back 9

Is a compound held together by ionic bonds

Remember that an ionic bond is formed through the transfer of electrons. These compounds are usually formed between +metals and -non-metals.

The ratio of cations to anions is always in a way that there is no net charge.

Front 10

Lattice Energy

Back 10

The way that the strength of ionic compounds is measured.

It is the energy released when one mole of an ionic compound is formed. This means when the individual ions of the compound come together to form the crystal lattice, they need less energy to stay together, so they release it, and the energy released is called the lattice energy

The bond force between ions of opposite charge is strongest when the ions are small.

The bond is also stronger as the charge on the ions get larger

So, the force of the bond between a +1 cation and a -1 anion isn't as strong as the force between a +3 cation and a -2 anion.

Front 11

Properties of Ionic Compounds (5)

Back 11

1. Form orderly crystals
2. High melting and boiling points (strength of ionic bonds
3. Hard and brittle (ionic bonds are strong and don't allow a lot of movement
4. Conduct electricity well
5. Good insulators

Front 12

Naming Binary Ionic Compounds Rules
Example NaCl

Back 12

1. The cation is always named first and gets its name from the name of the element
2. An anion also takes its name from its element, but it adds the suffix -ide to it

• Sodium Chloride

A simple binary compound is just what it seems - a simple compound with two elements in it.

Front 13

Naming Ionic Compounds Containing Transition Metals

Example: FeCl2, FeCl3

Back 13

1. Name the cation first
2. Followed by the anion with the suffix -ide added to the end of it.
3. Use Roman Numerals to account for the additional ions
   

• Iron (II) Chloride
• Iron (III) Chloride

A transition metal is a metal that can use the inner shell before using the outer shell to bond. These are the elements in the middle of the periodic table - things like zinc, iron and copper.

Front 14

Naming Polyatomic Ionic Compounds

Example: CIO, CIO2, CIO3, CIO4

Back 14

1. Name the cation
2. Name the anion -- if it can form more than one form of oxyanion, it gets a suffix of either -ate (for the smaller) or -ite (for the larger)
3. There are also suffixes for polyatomic ionic compounds when they are oxyanions, and have 3-4 types. The smallest would get a hypo- and the largest would get a per-

• hypochlorite
• chlorite
  
• chlorate
• perchlorate
• Nitrate

Polyatomic ionic compound: is a compound made up of a polyatomic ion, which is two or more atoms bonded together, and a metal

When a hydrogen ion is involved, the compound starts with either hydrogen or dihydrogen, depending on if there are one or two ions involved.

Front 15

Rules for Writing Chemical Formulas for Binary and Rolyatomic Ionic Compounds

Examples

Sodium oxide

Iron (III) oxide

Potassium phosphate

iron (III) chromate

Back 15

1. Write the symbols for the cation and the anion
2. Determine the charge on the cation and anion. If the cation has a Roman numeral after it, that is the charge on that cation.
   
3. Determine formula
   

• Na2O
• Fe2 O3.
  
• K3 PO4
  
• Fe2 (CrO4)3
  

Front 16

Covalent Compounds

Back 16

Is made when two or more nonmetal atoms bond by sharing valence electrons = Covalent Bond

Front 17

Nonmetals

Back 17

Are types of elements that lack metallic characteristics

• They are usually gases at room temperature
• They are poor conductors of heat and electricity and they gain electrons to form negative ions.
• Nonmetals are located to the far right of the periodic table, on the right side of the 'staircase.' Hydrogen is also a nonmetal, though it 'lives' in the top left of the periodic table.
  

Front 18

Types of Covalent Bonds

Single

Double

Triple

Back 18

Two shared electrons are known as a single covalent bond

Four shared electrons are known as a double bond

Six shared electrons are known as a triple bond

Front 19

Electronegativity

Back 19

The bonded electrons between two chlorine atoms are shared evenly - each atom exerts the same pull on the shared electrons. This isn't always the case

Is the ability of an atom to draw electrons to itself.

If a covalent bond is made between one atom that is really electronegative and another that is not, the electrons will not be shared evenly in the bond = dipole

Front 20

Dipole

Back 20

When electrons in a covalent bond are not shared evenly between the two atoms

Front 21

Properties of Covalent Bonds

Back 21

• Low boiling points
• Variously colored compounds
• Poor conductors of heat and electriciy
• Brittle solids

Front 22

Naming Simple Covalent Compounds

Examples

N20

SO3

N2H4

Back 22

1. The element that has the lower group number is listed first. If both elements are in the same group, list the element with the larger period first.
   
2. To name the first element, simply add a prefix to the name to indicate the number of that element present. If there is only one of the element, no prefix is necessary.
   
3. To name the second element, add a prefix to the element to indicate the number of that element present. Remove the last syllable of the element name and add '-ide.'
   
4. Diatomic compounds made of elements from the HOFBrINCl series are exceptions to our naming rules.

Dinitrogen monoxide

Sulfur trioxide

Dinitrogen tetrahydride

Front 23

Lewis Dot Polyatomic Ions

OH-

Back 23

The charge on a polyatomic atom indicates the number of electrons that have been lost or gained by a molecule -- you add this to the total of valence electrons for Lewis Dot Structures

Front 24

Resonance

Back 24

When a molecule or polyatomic ion has multiple valid Lewis dot structures

Resonance structures are shown together, separated by double headed arrows.