LESSON 14: AVODAGRO'S NUMBER
Avogadro's number
· Atoms and molecules are extremely small
· Macroscopic objects contains too many to count or weigh individually
· Amedeo Avogadro proposed that the number of atoms in 12.0g of Carbon be = to a constant (= to 1 mol of a Carbon)
· This value is now called Avogadro's number and forms the basis of all quantitative chemistry
· So what is Avogadro's number?
6.02 x 10^23
¤ 1.0 mol = 6.02 x 10^23
· One mole is simply a multiple of things
§ 1 pair = 2
§ 1 dozen =12
§ 1 century = 100
§ 1 mol = 6.02 x 10^23
HOW BIG IS A MOLE?
· 1 mole of meters would cross the entire galaxy over 3000 times
· 1 mole represents a huge number of particles
Example:· A sample of Nitrogen contains 1.56 x 10^23 atoms. How many mole of Nitrogen is this?
1.56 x 10^23 atoms x 1 mol
6.02 x 10^23 atoms
- 14.5 mole of I2 represents how many molecules?
14.5 mol x 6.02x10^23 molecules
1 mol
· How many Formula Units are present in 0.34 mol of CaCl2?
0.34 mol x 6.02 x 10^23 formula Units
1 mol
- Kelly
LESSON 13
Naming Compounds
Chemical Nomenclature
- today the most common system is IUPAC for most chemicals
-ions
-binary ionic
-polyatomic ions
-molecular compounds
-hydrates
-acids/bases
A) Chemical Formulas
- *be aware* of the difference between the ion and compound formulas
Zn - has a charge of 2+ (cations)
BaCl2 - the 2 represents the number of ions
Fe2
S3 - iron (|||) sulfide * some transition metals may have more
than 1 ion the roman numeral tell what charge it is
B) Multivalent Ions
- some elements can form more than one ion
eg. Iron --> Fe 3- or Fe 2-
Copper --> Cu 3+ or Cu 1+
- usually the top number (charge) is more commonly used
- IUPAC uses roman numerals in parenthesis to show the charge
- classical systems uses latin names of elements and the suffixes -ic (larger charge) and -ous (smaller charge)
eg. Ferric Oxide (iron)
- ic refers to the larger charge Fe 3-
Fe 2+ --> Fe
2 O
3
Other classical names
- Ferr - iron - Stann - tin
- Cupp - copper - Aunn - gold
- Mercur - mercury - Plumb - lead
C) Complex Ions
- complex ions are larger groups of atoms that stay together during a chemical reaction
- almost all are anions
- write the metal name and the polyatomic ion name
eg. sodium nitrate
NaNO3
rubidium phosphate
Rb3PO4
stannic nitride
Sn3N4
D) Hydrates
- some compounds can form lattices that bond to water molecules
- copper sulfate --> without the water molecule the compound
- sodium sulfate is preceded by 'anhydrous'
- these crystals contain water inside them which can be released by heating
- to name hydrates:
1. write the name of the chemical formula
2. add the prefix indicating the # of water molecules (mono- 1, di- 2)
3. add hydrate after prefix
eg. Ca(SO
3)
2 - 8H
2O - calcium sulphite octahydrate
Zn(NO
3) - 4H
2O - zinc nitrate tetrahydrate
E) Naming Acids and Bases
- hydrogen compounds are acids
- HCl --> hydrochloric acid
- hydrogen appears first in the formula unless it is part of a polyatomic group
sherilyn
LESSON 12
ELECTRON STRUCTURE
A) Electron Dot Diagram
- the nucleus is represented by the atomic symbol
- for individual elements it determines the number of valence electrons
- electrons are represented by the dots around the symbol
- 4 orbitals (one on each side of the nucleus) each holding a max. of 2 electrons
- each orbital get 1 electron before they pair up
B) Lewis Diagrams for Compounds and Ions
- in covalent compounds electrons are shared
- determine the # of valence electrons for each atom in the molecule
- place atoms so that the valence electrons are shared to fill each orbital
eg. NF3
Methane
C) Double and Triple Bonds
- sometimes the only way covalent compounds can fill all their valence level is if they share more than one electron
D) Ionic Compounds
- in ionic compounds electrons transfer from 1 element to another
- determine the number of valence on the cation. move these to the anion
- draw [ ] around the metal and non - metal
- write the charges outside the brackets
Magnesium oxide
Calcium Chloride
Sodium Chloride
Pictures re-done by: Kelly
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