1. 6.8 – NOTES Emperical Formulas

2. IV. Metallic Bonds and Properties of Metals
Electron sea model (delocalized electrons surrounding positive ions) metals do not bond ionically, do form lattices in the solid state
8 to 12 other metallic atoms will surround each metal atom
Forms a crowded condition, outer energy levels of the atom will overlap ;

3. The electron sea model suggests that the valence electrons are contributed to form a “sea”
This allows the electrons to move freely since they are not held to one specific atom
Because they are free to move they are referred to as “delocalized electrons”; a metallic cation forms (b/c the electrons are free-moving); a metallic bond is the attraction of the metallic cation for the delocalized electrons

4. 2. Properties of metals
1. MP – high, but BP very high (MP not as high b/c cations and electrons are already free moving, but BP requires atoms be removed from cations and electrons)
2. malleable/ductile – the “sea” of electrons is moved
3. conductors – movement of mobile electrons around metallic cations
4. delocalized electrons absorb and release photons of light giving metals a shiny appearance
5. hardness and strength increase as # of delocalized electrons increase;

6. Metal alloys
1. Definition - Alloys, amalgams metal – metal solution
2. Examples - brass (Cu + Zn), bronze (Cu + Sn), steel (Fe + C + Cr/Mn/others); amalgams – Hg based alloys; used to be found in dental work

7. V. Empirical Formula
A. Empirical formula
Definition – simplest, whole number ratio of atoms
If you know the percentage composition of a compound, then you will be able to determine the empirical formula (simplest ratio of elements) by using mole relationships.

8. Steps in the process:
1. Assume a 100 gram sample. Then each percentage is equal to grams. (e.g. 41% would become 41 g)
2. Change the grams to moles.
3. Determine the empirical formula by dividing all the moles by the smallest number of moles. If the empirical formula contains non- whole numbers, multiply all moles by a factor that makes all whole numbers.

9. Examples:
1. A compound of sulfur and oxygen is 50.0% sulfur and 50.0% oxygen by mass. What is the empirical formula?
S – 50.0g (1 mol/ 32.1 g) = / = 1
O – 50.0g (1 mol/ 16.0 g) = / = 2
SO2

10. 2. What is the empirical formula for a compound that contains 10
2. What is the empirical formula for a compound that contains 10.9% magnesium, 31.8% chlorine and 57.3% oxygen?
Mg – 10.9 g (1 mol/ 24.3 g) = / = 1 Know of any ions, Cl2O8?
Cl – 31.8 g (1 mol/ 35.5 g) = / = 2 How about ClO4?
O – 57.3 g (1 mol/ 16.0 g) = / = 8 Mg(ClO4)2?

11. N – 36.8 g (1 mol/ 14.0 g) = / = 1 x 2 = 2
O – 63.2 g (1 mol/ 16.0 g) = 3.95/ = 1.50 x 2 = N2O3
*1.5 cannot be rounded up, does not fall within .1/.9

12. C – 4.09 g (1 mol/ 12.0 g) = / = 1 x 3 = 3
H – g (1 mol/ 1.01 g) = 0.9 / = 2.64 x 3 = C3H8