1. Chapter 6 Section 1 Compounds and Molecules
Structure of Matter
Chapter 6 Section 1
Compounds and Molecules

2. Let’s Review! An element is made up of entirely the same atom
It is something that can not be broken down any further.
Compounds are pure substances composed of the same ions and/or molecules.
Compounds can be broken down into other substances.

3. Chemical Bonding Joining atoms to form new substances (molecules)
This is a chemical change, the new substances will have different properties than the original elements.
Chemical bonding involves valence electrons

4. Chemical Bonding
Atoms are most stable (happy) with a full valence shell.
A full valence is normally 8 e- (for H, He, Li and Be it is 2)
Bonding is when atoms share or transfer electrons in order to get to a full valence shell.

5. Chemical Structure
Chemical Structure: how the atoms are bonded together to make the compound
Water’s chemical formula, H2O, tells us WHAT is in it, but it doesn’t tell us HOW it is put together or how it acts.

6. Bond Length and Angle
Bond Length: the distance between nuclei of two bonded atoms
Bond Angle: the angle formed by two bonds to the same atom, tells which way these atoms point.

7. Chemical Compounds
Section 2

8. Let’s Recall… Why do atoms bond?
To have a stable electron configuration

9. Types of Bonds Three kinds of chemical bonds Ionic, Covalent, Metallic
The way a compound bonds determines many of its properties

10. Ionic Bonds
Ionic Bonding: a transfer of electrons (something gains, something loses)
Form from the attraction of oppositely charged ions
Ionic bonds occur between metals (cations) and nonmetals (anions)

11. Ionic Compounds
Ionic bonds are held together by electromagnetic force (opposites attract)
Compounds with ionic bonds are ionic compounds
Form networks, not molecules
For example
Na+ is attracted to Cl-
when large amounts get together, they stack in a crystal arrangement

13. Properties of Ionic Compounds
Examples of ionic compounds
Salts, baking soda, and rust
Brittle – tend to shatter when hit
High Melting points – most don’t melt until they are very hot
Solubility – many tend to dissolve in water.

14. Dissolving Ions
If you dissolve ions in water, they will break into parts, some with a positive charge, some with a negative charge
This difference in charge is why IONIC COMPOUNDS conduct electricity
Electrolyte: anything dissolved in water that increases conductivity

15. Covalent Bonds Covalent Bonding: a sharing of electrons
Usually between nonmetals

16. Covalent Bonds
Structural formula for a covalent bond is shown as a single line
More than one pair of electrons can be shared, and there will be an additional line for each pair shared

17. Covalent Bonds
Covalent bonds can also be shown with a Lewis Dot diagram
The valence electrons of the atom are drawn around the atom symbol
Bonded molecules are drawn with the dots being shared

18. Covalent Compound Covalent Compounds are made of molecules.
Molecules are atoms that share electrons in a bond.
Covalent compounds can be solids, liquids or gases

19. Properties of Covalent Compounds
Examples
Glass, rubbing alcohol, nitroglycerin, and natural gas
Low melting points – several exist as gases or liquids at room temperature.
Most covalent compounds do not dissolve in water or produce positive and negative particles if they dissolve.
Therefore most covalent compounds do not conduct electricity by themselves.

20. Metallic Bonding Bonds between metals
Sharing and transfer of electrons
Metallic bonds only occur with the same metal, not with others
Ca can bond with other Ca atoms, but not Ba

21. Metallic Bond
In metallic bonds, the valence electrons become community property, traveling anywhere they want to throughout the metal’s packed structure.
The outermost energy levels overlap, and the electrons are free to move from atom to atom
This “Sea of Electrons” is why metals are such good conductors of electricity and heat.

22. Compound Names and Formulas
Section 3

23. Remember: Valence electrons are the ones that want to react
Metals have fewer valence electrons, so they will give up 1, 2, or 3 electrons (cations)
Nonmetals have more valence electrons, they will gain 1, 2, or 3 valence electrons (anions)

25. Naming Ionic Compounds
Ionic bonds are between metals and nonmetals
The name of an ionic compound consists of the names of the ions in the compound
The metal is always named FIRST, and the nonmetal LAST

26. Naming Ionic Compounds
The cation (metal) name will remain the same
The anion (nonmetal) name will change
drop the ending and add “-ide”
For example – F-
fluoride
Cl-, O2-, C4-
chloride, oxide and carbide
Ions of chlorine and sodium give you
sodium chloride
(metal) (nonmetal)

27. Determining Formula of Ions
Ions have different charges
Ionic compounds want to have an overall charge of 0 (this makes them neutral and stable)
Total positive charge = total negative charge
For example:
Na+ and O2-
2 sodium for every one oxygen
Na2O

28. Determining Formula of Ions
Example: BORON OXIDE
Write the symbols of both elements (cation 1st, anion 2nd)
Write the valence of each as a superscript
Drop the positive and negative signs
Crisscross the superscripts so they become subscripts
Reduce when possible (not possible here)
B O
B3+ O2-
B3 O2
B3 O2
B2O3

29. Let’s Practice! Al3+ and O2- Al2O3 Aluminum oxide K+ and Cl- KCl
Potassium chloride
Sr2+O2-
Sr2O2  SrO
Strontium Oxide
The subscripts don’t effect the name if there is only one possibility

30. Determining Formula of Ions
Some metals form different cations with different charges
These are all metals that aren’t in group 1, 2 or aluminum – the transition metals!
The cation charge follows the symbol as a roman numeral
For example
iron can form Fe2+ or Fe3+
These are said as iron (II) and iron (III)
Cu+ and Cu2+
Copper (I) and Copper (II)

31. Covalent Naming
Covalent bonds involve shared electrons, so there are no charges
You still drop the ending of the second atom and replace it with the suffix “-ide”.
Ionic names ignored the subscript numbers.
Covalent does not
Prefixes are used in the name, they tell you how many atoms of the element are in the compound
You cannot reduce these formulas!

32. Prefixes prefix meaning *mono- 1 hexa- 6 di- 2 hepta- 7 tri- 3 octa- 8
tetra- 4
nona- 9
penta- 5
deca- 10
*“mono-”, it just keeps its original name!

33. Examples CO carbon monoxide CO2 carbon dioxide NI3 nitrogen triiodide
P4O6
tetraphosphorus hexoxide

34. Continuing I4O9 tetriodine nonoxide S2F10 disulfur decafluoride IF7
Iodine heptafluoride
Si2Cl6
disilicon hexachloride