Honors Chemistry
Chapter 4 notes—Formation of Compounds
I. The Variety of Compounds
A. Table Salt
1. Intro
a. Known as sodium chloride, found abundantly naturally
b. found in underground deposits and dissolved in the oceans
c. whether mined or evaporated it is not pure, so it is refined and put on your table
d. used as a food preservative, flavor enhancer, signals in the nervous system, melts snow
2. Physical properties of salt
a. white small crystalline solid
b. crystals are hard but brittle
c. melts around 800oC
d. solid NaCl doesn’t conduct electricity, liquid does
e. salt dissolves in water—the solution conducts electricity
3. Chemical properties of salt
a. Fairly unreactive
b. Stable or unreactive
4. Properties of sodium
a. shiny, silvery-white, soft, solid
b. melts at 98oC
c. must be stored under oil, otherwise it violently reacts with oxygen and water vapor
d. never found naturally by itself, it is always combined with other elements
5. Properties of chlorine
a. pale green, poisonous gas with a choking odor
b. slightly soluble in water and kills living cells, disinfectant for water supplies and pools
c. liquefies at -34oC
d. very reactive
e. needed for industrial process—bleach and plastics
f. transported in train tank cars, tanker trucks, and barges
6. sodium and chlorine react
a. reaction proceeds vigorously once it begins
b. once combined, becomes non-dangerous table salt
B. Carbon dioxide
1. Intro
a. colorless gas
b. major component of the air we and plants “breath” out--respiration
c. Plants take it in for photosynthesis
2. Physical properties
a. colorless, odorless, tasteless gas at room temperature
b. dry ice—solid form that forms at -80o C
c. no liquid form
d. soluble in water—pop
e. water solution conducts electricity
f. Coal and charcoal are mostly carbon
g. Denser than air—deprives fire of oxygen therefore
3. Chemical properties
a. relatively stable
b. photosynthesis is the most significant reaction
4. Properties of carbon
a. non-metal
b. unreactive at room temperature
c. higher temps reacts with many elements
d. charcoal is 90% carbon and obviously burns
e. form a wide variety of compounds, organic compounds
5. Properties of oxygen
a. colorless, odorless, tasteless gas
b. makes up about 21% of the air
c. supports burning
d. slightly soluble in water, fish respiration
e. becomes a liquid at -183oC
f. Oxygen is very reactive and forms oxides
g. most abundant element in the Earth’s crust
C. Water
1. Intro
a. dihydrogen monoxide
b. covers about 70% of the Earth’s surface
2. Physical properties
a. comes closest to being a universal solvent
b. transports dissolved materials
c. only one of three compounds that occurs in all three states naturally
d. boils at 100oC
e. freezes at 0oC
f. ice is less dense than liquid water (unusual)
g. insulator—does not conduct electricity
3. Chemical properties
a. stable
b. used in photosynthesis
4. Properties of Hydrogen
a. colorless, odorless, tasteless gas
b. lightest and most abundant element in the universe
c. usually labeled a non-metal
d. reactive—rarely found as a free element on Earth
e. condensates at -253oC
f. does not conduct electricity
g. slightly soluble in water
D. Using clues to make a case
1. atoms combine in different ways to from different compounds
2. these different compounds have different properties
3. compounds have different properties than the elements that make them up
II. How elements form compounds
A. Atoms collide
1. Better rendition, come in contact
2. Their electron clouds or valence electrons are coming into contact
B. Chemical stability
1. Chemical stability is achieved by having a full outer shell
2. Generally speaking this is 8 valence electrons
3. Octet rule—an atom becomes stable by obtaining a full outer level which is usually 8 (H and
He are the major exceptions)
4. Can also be called achieving a noble gas configuration
C. Ways to Achieve Stability
1. Ionic bonding—Electrons are transferred
a. atoms create ions
b. ions bond because of opposite charges
c. ion—charged particle
1) anion—a negative ion
2) cation—a positive ion
d. Crystalline structure—a regular repeating arrangement of atoms, ion, or molecules
1) crystal—this structure
2) formula unit—the repeating pattern, also used as the formula
e. Strong attractive forces which give definitive solid shapes with high melting points
f. Brittle—they shatter
2. Covalent bonding—Electrons are shared
a. atoms share to gain full shells
b. molecules are discreet particles with little interaction with other particles
c. we use sticks to represent pairs of shared electrons
d. there can be single, double, and triple bonds (rarely quadruple)
D. How do ionic and covalent compounds compare
1. Ionic compounds
a. generally solids with high melting points, high attractive forces across the board
b. they are hard, rough, and brittle
c. soluble in water
d. conduct electricity when dissolved or melted
e. electrolyte—any compound that will conduct electricity when dissolved or melted
2. Covalent compounds
a. generally liquids or gases with low melting points
1) high attractive forces between sharing atoms
2) relatively low attractive forces between molecules
b. most are not soluble in water
c. most are flexible
d. do not conduct electricity in any form