1. Chemical Bonds
Chapter 22

2. Stability in Bonding
Section 1

3. Properties of Combined Elements
When combining elements, new properties emerge
Copper is a shiny, copper colored metal
Sulfur is pale, yellow solid
Oxygen is a colorless, odorless gas
Copper Sulfate (Cu2SO4) is a blue crystalline salt that is used in pesticides

4. Formulas Formulas are like recipes A chemical formula will tell you
What elements are included
The exact number of atoms of each element are found in a unit of that compound
Subscripts are used to show how many of each atom are present
Changing the subscript changes the compound

5. Some Familiar Compounds
Familiar Name
Chemical Name
Formula
Sand
Silicon dioxide
SiO2
Milk of Magnesia
Magnesium hydroxide
Mg(OH)2
Cane Sugar
Sucrose
C12O22O11
Lime
Calcium oxide
CaO
Vinegar
Acetic acid
CH3COOH
Laughing Gas
Dinitrogen oxide
N2O
Grain Alcohol
Ethanol
C2H5OH
Battery Acid
Sulfuric acid
H2SO4
Stomach Acid
Hydrochloric acid
HCl

6. Atomic Stability
Electrons in the outer energy level of an atom are considered the bonding electrons
Bonding electrons are called valence electrons
An atom is considered stable when it has 8 electrons in its outer shell
An atom with 8 electrons in its outer energy level will NOT form bonds (except Period 1 elements)
The noble gases will not form bonds are considered inert

7. The Quest to be Noble
Atoms of elements that don’t naturally have 8 electrons in the outer energy level will lose, gain, or share electrons to become stable
Sodium will give an electron away
Chlorine will take an electron
Atoms that that gain or lose electrons become ions
Ions are charged particles because they have either fewer or greater electrons than protons

8. Ions Positively charged ions are called cations
Ca+2, Na+1
Metals will form cations
Negatively charged ions are called anions
O-2, N-3
Non-metal will form anions

9. Ionic Bonds

10. Chemical Bonds
When atoms give, take, or share electrons chemical bonds are formed
A chemical bond is a force that holds atoms together in a compound.
Remember: Compounds will have different physical and chemical properties that the atoms that make them up
The two types of chemical bond that form compounds are
Ionic
Covalent

11. Ionic Bonding Atoms are in constant motion
When two or more atoms collide they may form a bond
In ionic bonding, the collision results in one atom taking an electron(s) from the other
Ionic bonding results from the transfer of electrons
Ionic bonds will always involve a metal atom transferring its electrons to a non-metal atom
The transfer of electrons in ionic bonds result in the release of large amounts of energy

12. Ionic Bonds Let’s take potassium (K) Now consider Iodine (I)
1 electron in its outer energy level (4th level)
Becomes stable by giving an electron away so that its 3rd level, the new outer level, will be full
Now consider Iodine (I)
7 electrons in its outer shell
Will need one more electron to fill its outer energy level
In a collision, Iodine will take Potassium’s electron
Potassium and Iodine are now ions
They have opposite charges
Charges are known as oxidation numbers
The attract one another and form an ionic bond (KI)

13. Ionic Bonds and Net Charge
The end result of an ionic bond is a net charge on the compound of 0
Potassium ended up with a charge of +1
Iodine ended up with a charge of -1
KI has a net charge of 0 because the charges cancel

14. Ionic Bonds Ionic bonds can involve more than one electron
Let’s consider Magnesium (Mg)
Metal
Has two electrons in its outer shell
Will give up both electrons to achieve stability
Will form a +2 cation
Now for Chlorine (Cl)
Non-metal
Has seven electrons in its outer shell
Only needs on electron to achieve stability
Will form a -1 anion
Magnesium will give one electron to two different Chlorine atoms
MgCl2
2 + (– 1) + (–1) = Net charge of 0

15. Writing Ionic Formulas
Write the symbol of the element that has the positive oxidation number or charge first
Write the symbol of the element with the negative oxidation number or charge second
Balance the charges

16. Naming Ionic Compound Write the name of the cation
Write the root name of the negative ion
Add –ide to the root

17. Special Metal Ions
Many of the transition metals can form more than one ion
Ions for transition metals that have more than one ion are designated using Roman numerals
The Roman numeral is equal to the charge on the ion
Name
Oxidation Number
Copper (I) 1+
Copper (II) 2+
Iron (II)
Iron (III) 3+
Chromium (II)
Chromium (III)
Lead (II)
Lead (IV) 4+

18. Writing Formulas and Naming Compounds with Special Ions
Copper (II) Oxide
Cu 2+
O 2-
CuO
Chromium (III) chloride
Cr 3+
Cl -1
CrCl3
CuCl2
What is the charge on the anion? -1
What is the total negative charge? -2
So what must the charge on the cation be? +2
So it must be Copper (II)
Include the Roman numeral in the name
Copper (II) chloride

19. Compounds with Polyatomic Ions
Not all compounds are binary
Some are polyatomic
“poly” means many
A polyatomic ion is a positively or negative charged, covalently bonded group of atoms
They act as a single ion

20. Naming & Writing Compounds with Polyatomic Ions
To name a compound that contains a polyatomic, just use the name of the polyatomic ion whenever it appears
Do not add –ide if using a polyatomic anion
If more than one polyatomic atom is used, put parenthesis around the atom before using the subscript
Charge
Name
Formula 1+
ammonium
NH4+ 1-
Acetate
Chlorate
Hydroxide
Nitrate
C2H3O2-
ClO3-
OH-
NO3- 2-
Carbonate
sulfate
CO32-
SO42- 3-
Phosphate
PO43-

21. Naming & Writing Compounds with Polyatomic Ions
Ammonium phosphate
Ammonium
NH4+
Phosphate
PO4 3-
You need three ammonium ions for every one phosphate ion
(NH4)3PO4
Calcium Chlorate
Calcium
Ca+2
Chlorate
ClO3-
You need two chlorate ions for every calcium ion
Ca(ClO3)2

22. Compounds with Added Water
Some ionic compounds have water molecules as part of their structure
They are called hydrates
The water can be removed if heated
The resulting crystals are anhydrous
Anhydrous means “without water”
Hydrates have water chemically attached to its ions and written into its chemical formula

23. Naming Hydrates CoCl2 • 6H20 CaSO4 • 2H20 Cobalt chloride hexahydrate
Calcium sulfate dihydrate
Name
Number of Atoms
Mono- 1
Di- 2
Tri- 3
Tetra- 4
Penta- 5
Hexa- 6
Hepta- 7
Octa- 8
Name
Number of Atoms
Mono- 1
Di- 2
Tri- 3
Tetra- 4
Penta- 5
Hexa- 6
Hepta- 7
Octa- 8

24. Covalent Bonding

25. Covalent Bonding Form between two non-metals
When two non-metals bond, neither is very willing to give up its electrons
They end up sharing electrons
A compound that results form a covalent bond is called a molecule

26. Single Covalent Bonds Involves sharing two electrons
Water has two single bonds
Each hydrogen atom contributes one electron
Oxygen provides one for sharing to each hydrogen atom

27. Multiple Bonds
A covalent bond can also contain more than one pair of shared electrons
Double Bonds
Involve 4 electrons O2
Each oxygen needs two electrons
Triple Bonds
Involve 6 electrons N2
Each nitrogen needs three electrons

28. Polar Bond Electrons are not always shared equally
The strength of the attraction of each atom to its outer electrons is related to its size
The further the electron is away from the nucleus, the weaker the attraction
The larger the nucleus the greater the attraction
The electrons will spend more time near the stronger atom
A partial negative sign is assigned to the stronger atom
A partial negative sign is assigned to the weaker atoms

29. Polar vs Nonpolar
Molecules that don’t share their electrons equally are called polar molecules
Water
Molecules that share their electrons equally are non-polar
Non-polar molecules are more symmetrical or involve bonding of two identical molecules
CCl4 O2

30. Naming Binary Covalent Compounds
The prefixed used in naming hydrates are used when naming binary covalent compounds
Mono- is often omitted from the formula name
The last vowel of the prefix is dropped if the second element begins with a vowel
The second element still ends in -ide
N2O
Dinitrogen dioxide
N2O5
Dinitrogen pentoxide

31. Properties of Compounds
Covalent Compounds
Bonds are strong but attraction between molecules is weak
Melting points and boiling points are lower
Will be solid, liquid, or gas
Solid form will be soft
Poor electrical and thermal conductors
Ionic Compounds
Bonds are strong
Higher melting points
Higher boiling points
Hard and brittle solids
Dissolved in a liquid, they will conduct electricity