1. CHEMICAL BONDS
CHAPTER 7,8

2. CHAPTER 7 CHEMICAL BONDS
6.1
IONIC BONDING
6.2
COVALENT BONDING
6.3
NAMING COMPOUNDS & WRITING FORMULAS
6.4
THE STRUCTURE OF METALS

3. Objectives Identify when an atom is unlikely to react
Ionic Bonding
Identify when an atom is unlikely to react
Identify one way in which elements can achieve stable electron configurations
Determine how the structure of an ionic compound affect its properties

4. CHAPTER 7 CHEMICAL BONDS
Ionic Bonding
Bonding
Why are Noble Gases inert (nonreactive)?
Stable electron configuration – the highest occupied energy level of the noble gas atom is filled.
Eight valence electrons in the case of all Noble gases
Except Helium(He), which has two…however is still filled
Other elements tend to react to achieve the same stable electron configuration as the Noble Gases…
filled outermost energy levels.

5. CHAPTER 7 CHEMICAL BONDS
Ionic Bonding
Electron Dot Diagrams
An electron dot diagram is a model of an atom in which each dot represents a valence electron, and the element symbol represents the nucleus and all other electrons of the atom.
Examples:

6. CHAPTER 7 CHEMICAL BONDS
Ionic Bonding
Ionic Bonds – Transfer of Electrons
Atoms of elements that do not have a complete set of valence electrons tend to react with other atoms to form stable electron configurations.
Some elements do this by a transfer of electrons: Ionic bonding.
When an atom gains or loses electrons, the number of protons and electrons is no longer equal. It now has a net positive or negative charge and is an ion. An ion is a charged atom.

7. CHAPTER 6 CHEMICAL BONDS
Ionic Bonding
Ionic Bonds – Formation of Ions
Cations = Positve Charge
If an ion has more protons than electrons, it has a net positive charge, and is called a cation.
Represented by a superscript plus sign to the right of the element symbol. Example : Na+
Named after their elements. For example, Na+ is called the sodium ion.
Anions = Negative Charge
If an ion has more electrons than protons, it has a net negative charge, and is called a anion.
Represented by a superscript minus sign to the right of the element symbol. Example : Cl-
Named by using part of the element name plus the suffix -ide. For example, Cl- is called the chloride ion.

8. CHAPTER 6 CHEMICAL BONDS
Ionic Bonding

9. CHAPTER 6 CHEMICAL BONDS
Ionic Bonding
Formation of Ionic Bonds
OPPOSITES ATTRACT: Once ions are
formed from the transfer of electrons, the
positive and negative ions are attracted to
each other and form chemical bond.
A chemical bond is the force that holds
atoms or ions together as a unit.
An ionic bond is the force that holds anions
and cations together.

10. CHAPTER 6 CHEMICAL BONDS
Ionic Bonding

11. CHAPTER 7 CHEMICAL BONDS
Ionic Bonding
Ionization Energy
For an atom to lose an electron, the electron must gain enough energy to overcome its attraction to the positive nucleus.
The amount of energy required to remove an electron is called ionization energy. It varies from element to element.
The lower the ionization energy (IE), the easier it is to remove an electron from an atom.

12. CHAPTER 7 CHEMICAL BONDS
Ionic Bonding
Ionization Energies of the
A Group Elements
Which group has the highest ionization energies? Why?
Which group has the lowest ionization energies? Why?
Which element has the lowest ionization energy? Why?
Which element has the highest ionization energy? Why?

13. CHAPTER 7 CHEMICAL BONDS
Ionic Bonding
Ionic Compounds
Ionic compounds (contain ionic bonds) can be represented by chemical formulas
Chemical Formula:
Shows elements in a compound with element symbols
Gives ratios of atoms or ions in the compound via subscripts
If only one atom of an element is present, no subscript is required
Examples: NaCl MgCl2

14. CHAPTER 7 CHEMICAL BONDS
Ionic Bonding
Properties of Ionic Compounds
Tend to form crystal lattices (repeating patterns of ions resulting from attractions between positive and negative ions.)
Properties of ionic compounds can be explained by strong attractions among ions in a crystal lattice.
High melting point (a lot of energy required to break attractions between ions.)
Solid state is brittle (pushing like ions together causes them to repel in a “rebound effect”)
Solid has poor conductivity (ions can’t move), but liquid state has high conductivity (ions can move)

15. CHAPTER 7 CHEMICAL BONDS
Ionic Bonding
Bonding Basics Worksheet
Write the electron dot diagram (Lewis Structure) for each element.
Use one color for the electrons in metals, and another color for the electrons in nonmetals.
Draw an arrow (or more if needed) with a different color to show the transfer of electrons, and move the colored dot to the new location.
Determine the charge for each ion and write the formula.
Make sure the sum of the oxidation numbers is zero and write the chemical formula.

16. Objectives Covalent Bonding
Determine how atoms are held together in a covalent bond
Identify what happens when atoms don’t share electrons equally
List the factors that determine whether a molecule is polar
Compare and contrast the attractions between polar and nonpolar molecules

17. CHAPTER 8 CHEMICAL BONDS
Covalent Bonding
Covalent Bonds
Covalent Bonds (Co- means “to share” / -valent refers to valence electrons)
Chemical bond in which two atoms share a pair of valence electrons
Attractions between shared electrons and the protons in each nucleus hold the atoms together
Molecule: a neutral group of atoms joined by one or more covalent bonds
Multiple covalent bonds: sometimes 2 atoms can share more than one pair of electrons
2 shared pairs: double bond (4 electrons total are shared )
3 shared pairs : triple bond (6 electrons are shared)
O O O2

18. CHAPTER 8 CHEMICAL BONDS
Covalent Bonding
Covalent Bonds
Representation (example: hydrogen gas, or H2)
Electron Dot diagram
Structural Formula (dash represents a pair of shared electrons)
For Multiple bonds, multiple lines between two atoms would be used.
ELECTRON DOT DIAGRAM H H

19. CHAPTER 8 CHEMICAL BONDS
Covalent Bonding
Covalent Bonds
Representation (example: hydrogen gas, or H2)
Electron Dot diagram
Structural Formula (dash represents a pair of shared electrons)
For Multiple bonds, multiple lines between two atoms would be used.
ELECTRON DOT DIAGRAM H H

20. CHAPTER 8 CHEMICAL BONDS
Covalent Bonding
Covalent Bonds
Representation (example: hydrogen gas, or H2)
Electron Dot diagram
Structural Formula (dash represents a pair of shared electrons)
For Multiple bonds, multiple lines between two atoms would be used.
ELECTRON DOT DIAGRAM H H
Shared Electrons

21. CHAPTER 8 CHEMICAL BONDS
Covalent Bonding
Polar vs Nonpolar Bonds
Unequal sharing of electrons
Some atoms have a greater attraction for electrons
Electronegativity: the ability of an atom to attract electrons to itself in a covalent bond.
Polar Covalent Bond
Electrons shared UNEQUALLY between 2 atoms
The two atoms have DIFFERENT electronegativities
Nonpolar Covalent Bond
Electrons shared EQUALLY between 2 atoms
The two atoms have SIMLAR electronegativities.

22. CHAPTER 8 CHEMICAL BONDS
Covalent Bonding
Polar Molecules
Polar molecules have partial positive and negative charges at opposite ends (like a magnet has North and South poles)
Partial negative charge: δ-
Partial positive charge:δ+
Polarity of a molecule is determined by
Type of covalent bonds (polar or nonpolar)
Shape of molecule
Polar molecule
Nonpolar molecule

23. CHAPTER 8 CHEMICAL BONDS
Covalent Bonding
Attraction Between Molecules
All molecules have a force of attraction between them.
Attractions between polar molecules like water, are stronger than those between nonpolar molecules
In water, these attractions are called hydrogen bonds (partial positive hydrogen ends attract partial negative oxygen ends)
This explains many of water strange and
important properties:
High surface tension
High adhesion and cohesion
Lower density in solid state (ice floats!)

24. Objectives
Naming Compounds & Writing Formulas
List the information that the name and formula of an ionic compound provide
Determine what information does the name and formula of a molecular compound provide

25. CHAPTER 7 CHEMICAL BONDS
Naming Compounds & Writing Formulas
Naming Ionic Compounds
A compound made from only two elements is a binary ionic compound.
Naming ionic compounds is easy:
It’s the name of the cation (positive ion)
Followed by the name of anion (negative ion), it has the suffix –ide.
Let’s take calcium and iodine as an example:
Calcium is the name of the cation and, iodide is the name of the anion, therefore: calcium iodide

26. CHAPTER 7 CHEMICAL BONDS
Naming Compounds & Writing Formulas
Writing Ionic Compounds
Once again let’s look at calcium iodide:
What are their oxidation numbers?
Cross them (only the numbers…no charges!)
Don’t write ones!
Rewrite the formula Ca I
CaI2

27. CHAPTER 7 CHEMICAL BONDS
Naming Compounds & Writing Formulas
Describing Ionic Compounds
The following are two substances, both made with compounds of copper and oxygen.
The name of an ionic compound must distinguish the compound from other ionic compounds containing the same elements.
Copper (I) oxide – Cu2O
Copper (II) oxide – CuO

28. CHAPTER 7 CHEMICAL BONDS
Naming Compounds & Writing Formulas
Metals with Multiple Ions
Remember an Ion is: a charged atom
Many transition metals form more than one type of ion.
When a metal forms more than one ion, the name of the ion contains a Roman numeral to indicate the charge on the ion.

29. CHAPTER 7 CHEMICAL BONDS
Naming Compounds & Writing Formulas
Copper and Oxygen
Copper (I) oxide
Copper (II) oxide
+1 -2
+2 -2
Cu O
Cu O
Cu2O
Cu2O CuO

30. CHAPTER 7 CHEMICAL BONDS
Naming Compounds & Writing Formulas
Polyatomic Ions
A polyatomic ion is a covalently bonded group of atoms that has a positive or negative charge, and acts as a single unit (like an ion).
The prefix poly- means many
Most polyatomic ions are anions,
which means they will have a
negative charge.
Sometimes parentheses are used
in a formula to denote the number
of polyatomic ions are included
within that formula.

31. CHAPTER 7 CHEMICAL BONDS
Naming Compounds & Writing Formulas
Naming & Writing Compounds with Polyatomic Ions
Let’s look at calcium and phosphate (a polyatomic ion)
NOTHING CHANGES!, follow the same steps as before!
What are their oxidation numbers?
Cross them. (Only the numbers, NO CHARGES)
Don’t write ones!
Rewrite the formula.
Use parentheses if necessary
The name of this compound is:
calcium phosphate
Ca PO4
Ca3(PO4)2
Ca3PO42

32. CHAPTER 7 CHEMICAL BONDS
Naming Compounds & Writing Formulas
Math Practice
Write the formula for the compound calcium oxide.
Write the formula for the compound copper(I) sulfide.
Write the formula for the compound sodium sulfate.
Write is the name of the compound whose formula is NaOH?
CaO
Cu2S
Na2SO4
sodium hydroxide

33. CHAPTER 8 CHEMICAL BONDS
Naming Compounds & Writing Formulas
Describing Molecular Compounds
Molecular compounds are those compounds formed by sharing electrons, covalently bonded.
The name and formula of a molecular compound describe the type and number of atoms in a molecule of the compound.
The general rule is the most metallic element appears first in the name.
If both elements are in the same group, the more metallic element is closer to the bottom of the group.
The name of the second element is changed to end in the suffix
–ide. (as in carbon dioxide)

34. CHAPTER 8 CHEMICAL BONDS
Naming Compounds & Writing Formulas
Naming Molecular Compounds
Number of Atoms
Prefix 1
mono- 2
di- 3
tri- 4
tetra- 5
penta- 6
hexa- 7
hepta- 8
octa- 9
nona- 10
deca-
When naming molecular compounds prefixes are used to denote the number of atoms of each element within the molecule.
The prefix mono- is often is not used for the first element in the name.
N2O4
dinitrogen tetroxide

35. CHAPTER 8 CHEMICAL BONDS
Naming Compounds & Writing Formulas
Naming Molecular Compounds
Number of Atoms
Prefix 1
mono- 2
di- 3
tri- 4
tetra- 5
penta- 6
hexa- 7
hepta- 8
octa- 9
nona- 10
deca-
P2O5
diphosphorus pentoxide CO
carbon monoxide

36. CHAPTER 8 CHEMICAL BONDS
Naming Compounds & Writing Formulas
Writing Molecular Compounds
Number of Atoms
Prefix 1
mono- 2
di- 3
tri- 4
tetra- 5
penta- 6
hexa- 7
hepta- 8
octa- 9
nona- 10
deca-
carbon tetrafluoride
CF4
pentaphosphorus decoxide
P5O10

37. CHAPTER 8 CHEMICAL BONDS
The Structure of Metals
What are the forces that give a metal its structure as a solid?
How do metallic bonds produce some of the typical properties of metals?
How are the properties of alloys controlled?