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Fundamental Chemical Laws
These laws led to the discovery that all matter is composed of atoms
(1) Law of Conservation of Mass Frenchman Antoine Lavosier Matter can’t be created or
destroyed
Fundamental Chemical Laws cont… (2) Law of Definite Proportion (Constant
Composition) Frenchman Joseph Proust A compound always contains the same
percentage by mass of each element in it.
For example all samples of CO2 will always be 1 part C (12.01 g C) to 2 parts O (32 g O)
Fundamental Chemical Laws cont… (3) Law of Multiple Proportions Englishman John Dalton When two elements will form more
than one compound those two elements will always combine in whole-number ratios
For example: 1 gram of oxygen will combine with 1.750, 0.875, or 0.4375 grams of nitrogen
Dalton’s Atomic Theory Elements are made of tiny particles called
atoms All atoms of a given element are identical,
atoms of different elements are different Chemical compounds form when atoms of
different elements combine with one another
A chemical reaction merely involves the rearrangement of atoms, hence mass is conserved
Atomic Theory History The electron Discovered by J.J. Thomson during experiments
with cathode ray tubes Cathode Ray tube The same results were obtained regardless of
various metals being used as the electrodes. The same amount of deflection
Since all atoms are neutral he proposed there must be an equal amount of positive charge in atoms
But he did not discover the source of positive charge Plum-pudding model of the atom
Atomic Theory History cont…
The source of positive charge was discovered by Thomson’s student Ernest Rutherford.
Rutherford is best remembered for his Gold – Foil Experiment
Demonstration of the Experiment
Atomic Theory History cont… Millikan’s Oil Drop Experiment allowed for
the calculation of the charge of an individual electron
The Oil Drop Experiment By varying the voltage in the two plates
Millikan could determine the amount of charge needed to counterbalance the force of gravity. Using this information with the known charge to mass ratio of the electron, he could calculate the mass of an electron.
9.11 x 10-31 kg
The Modern View of Atomic Structure
The atom contains a tiny nucleus approximately 10-13 cm in diameter with electrons circling it at a distance of about 10-8 cm from the center
Protons and neutrons make up the nucleus and are held together by the strong nuclear force
The Modern View of Atomic Structure
Mass of subatomic particles Charge of subatomic particles While all atoms are composed of
the same components it is the arrangements of the electrons that give atoms their different chemical properties
The Modern View of Atomic Structure
Writing the symbol of the elements and counting the number of protons, neutrons, and electrons
The same atom with a different number of neutrons and hence mass are known as isotopes
Molecules and Ions Atoms are held together in compounds by chemical
bonds Chemical bonds fall into 2 major categories (there are
others, but for now we will focus on only these two) Covalent bonds – sharing of electrons between atoms
resulting in molecules Ionic bonds – resulting from a transfer of electrons from
one atom to another. The resulting ions formed are attracted to one another forming an individual unit cell (not a molecule)
The compounds formed from ionic bonds are known as salts
Nomenclature of inorganic compounds
Simple binary ionic compounds Type 1 – when the cation only forms
one charge Cations keep their names Anions have the end of their name
changed it ide Examples:
Nomenclature of inorganic compounds Simple binary ionic compounds
Type II – when the cation forms more than one charge
Cation must be identified by following it with a Roman numeral to represent the charge on the cation
Anion ending is still just change to ide Examples
Nomenclature of inorganic compounds
Ionic compounds that contain polyatomic ions The same rules for ionic compounds
already introduced still apply The polyatomic ions name is never
changed Examples
Nomenclature of inorganic compounds Covalent compounds Use prefixes Mono, di, tri, tetra, penta, hexa, hepta,
octa, nona, deca The first element only gets a prefix if
there is more than one The second element always gets a prefix Examples
Simple Organic Compounds Hydrocarbons
Nothing but carbon and hydrogen Methane, ethane, propane,
pentane, hexane, heptane, octane, nonane decane
Formula is CnH(2n + 2)
All of these fit into a category known as alkanes
Simple Organic Compounds Alkenes
Hydrocarbon with a double bond CnH2n
Examples Alkynes
Hydrocarbon with a triple bond CnH(2n – 2)
Examples
Hydrocarbon Derivatives Alcohols Hydrocarbons with one of the H’s of the
end removed and replaced with OH The OH is called a hydroxyl group and is not
to be confused with the hydroxide ion that has a 1- charge on it.
Same name just change the ending to ol Examples
Naming Acids
Non- Oxygen Acids Give a prefix hydro and a suffix ic
followed by the word acid Examples
HCl, HCN, HBr, HI, HF
Oxyacids Contain a polyatomic ion If the polyatomic ion end in ate change
the ending to ic Examples H2SO4, H3PO4, HC2H3O2, HClO4
If the polyatomic ion ends in ite change the ending to ous Examples H2SO3, H3PO3, HNO2, HBrO2