1. IONIC COMPOUNDS
Chapter 8

2. Forming Chemical Bonds Section 8.1
The force that holds two atoms together is called a chemical bond.
Chemical bonds may form by the attraction between a positive nucleus and negative electrons or the attraction between a positive ion and a negative ion

3. Review…
Valence electrons are the electrons in the outermost energy level. These same electrons are involved in the formation of chemical bonds between two atoms

4. Electron-Dot Structures
Especially useful when illustrating formation of chemical bonds!!

5. From Chapter 6…
Ionization energy refers to how easily an atom loses an electron.
Noble gases, having high ionization energies, show a general lack of chemical reactivity
The difference in reactivity is directly related to the valence electrons
Elements tend to react to acquire the stable electron structure of a noble gas (V.E. 8)

6. Formation of Positive Ions
A positive ion forms when an atom loses one or more valence electrons in order to attain a noble gas configuration
Positively charged ion is called a cation

7. Transition Metals
When forming positive ions, transition metals commonly lose their valence electrons, forming 2+ ions.
However, it is also possible for d electrons to be lost
A useful rule of thumb for these metals is that they form ions with a 2+ or 3+ charge.

8. Negatively charged ion is called an anion
Nonmetals have a great attraction for electrons and from stable outer electron configuration by gaining electrons
Negatively charged ion is called an anion

9. Checkpoint Why do ions form?
Describe the formation of positive and negative ions.
Predict the change that must occur to achieve noble gas stability
Nitrogen
Sulfur
Barium
Lithium

10. Answers Atoms gain stability by losing or gaining electrons
Positive ions form when atoms lose valence electrons
Negative ions form when valence electrons are added to an atom
Nitrogen- gain 3 electrons (N3-)
Sulfur- gain 2 electrons (S2-)
Barium- lose 2 electrons (Ba2+)
Lithium- lose 1 electron (Li1+)

11. The Formation and Nature of Ionic Bonds (Section 8.2)
The electrostatic force that holds oppositely charged particles together in an ionic compound is referred to as an ionic bond
Ionic bonds form between cations (+) and anions (-)
Binary compounds contain two different elements
Metallic cation
Nonmetallic anion
Electrons gained = electrons lost
OVERALL CHARGE OF THE COMPOUND FORMED MUST BE ZERO!!!

12. Properties of Ionic Compounds
High Melting and boiling points (indicating strong bond strength)
Most are crystalline solids at room temperature
ions in a regular, geometric pattern (crystal lattice)
hard, brittle
conduct electricity when molten or dissolved in water (aka electrolyte)

13. Names and Formulas for Ionic Compounds (Very Important!) Section 8.3
Terms to be familiar with:
Formula Unit- the simplest ratio of the ions represented in an ionic compound
Monatomic Ion- a one-atom ion (Mg2+ or Br1-)
Oxidation Number- the charge of the monatomic ion
Polyatomic Ion- ions made up of more than one atom (i.e. Nitrite= NO2-)

14. Magnesium and chlorine Aluminum and bromide Cesium and nitride
Write the correct formula for the ionic compound composed of the following pairs of ions
Potassium and iodine
Magnesium and chlorine
Aluminum and bromide
Cesium and nitride

15. Answers 1. Potassium and iodine K+1 and I-1  KI (1:1 ratio)
2. Magnesium and chlorine
Mg+2 and Cl-1  MgCl2 (1:2 ratio)
3. Aluminum and bromide
Al+3 and Br-1  AlBr3 (1:3 ratio)
4. Cesium and nitride
Cs+1 and N-3  Cs3N (3:1 ratio)

16. Compounds Containing Polyatomic Ions
The charge given to a polyatomic ion applies to the entire group of atoms
The polyatomic ion acts as an individual ion
NEVER CHANGE THE SUBSCRIPTS WITHIN THE ION
If more than one polyatomic ion is needed, place parentheses around the ion and write the appropriate subscript outside the parentheses.

17. Practice Problems Calcium and Nitrate Aluminum and Hydroxide
Barium and Sulfate
Sodium and Phosphate
Potassium and Sulfate

20. Naming Ionic Compounds
Oxyanion- a polyatomic ion composed of an element, usually a nonmetal, bonded to one or more oxygen atoms
An ion with more oxygen atoms is named using the root of the nonmetal plus the suffix –ate (ex. NO3-  nitrate)
An ion with fewer oxygen atoms is named using the root of the nonmetal plus the suffix –ite (ex. NO2-  nitrite )

21. Chlorine’s 4 Oxyanions ClO4-  perchlorate (most oxygen's)
ClO3-  chlorate (one less oxygen)
ClO2-  chlorite (two fewer oxygen's)
ClO-  hypochlorite (three fewer oxygen's)

22. Naming Ionic Compounds
Name the cation (+) first and the anion (-) second.
Monatomic cations use the element name.
Monatomic anions take their element name plus the suffix –ide.

23. 4. Group 1A and Group 2A metals have only one oxidation number (charge). Transition metals and metals on the right side of the periodic table often have more than one oxidation number.
The oxidation number is written as a Roman numeral in parentheses after the name of the cation
5. If the compound contains a polyatomic ion, simply name the ion.

24. Practice problems
NaBr
CaCl2
KOH
Cu(NO3)2
Ag2CrO4

25. Cation + Anion NaBr  sodium bromide CaCl2  calcium chloride
KOH  potassium hydroxide
Cu(NO3)2  copper (II) nitrate
Ag2CrO4  silver chromate

26. Section Review Anion Cation  Oxide Chloride Sulfate Phosphate
Potassium
Barium
Aluminum
Ammonium

27. Answers Anion Cation  Oxide Chloride Sulfate Phosphate Potassium K2O
KCl
K2SO4
K3PO4
Barium
BaO
BaCl2
BaSO4
Ba3(PO4)2
Aluminum
Al2O3
AlCl3
Al2(SO4)3
AlPO4
Ammonium
(NH4)2O
NH4Cl
(NH4)2SO4
(NH4)3PO4

28. Metallic Bonds and Properties of Metals (Section 8.4)
Although metals do not bond ionically, they often form lattices in the solid state.
Electron sea model- all the metal atoms in a metallic solid contribute their valence electrons to form a “sea” of electrons

29. The electrons present in the outer energy levels of the bonding metallic ions are not held by any specific atom and can move easily from one atom to the next. (Delocalized electrons)
A metallic bond is the attraction of a metallic cation for delocalized electrons

30. Metal Alloys A mixture of elements that has metallic properties
Substitutional- atoms of the original metallic solid are replaced by other metal atoms of similar size
Brass, pewter, 10-carat gold, and sterling silver
Interstitial- formed when small holes in a metallic crystal are filled with smaller atoms
Carbon steel
Great test question…