chemistrynotes

Notes for the Second Test

Material to study from may also be found in your book on chapters 2, 16, 20, 21 and 23.

The Atom:
Over the years the model of the atom has evolved as our technology has evolved.

The Greeks said that when you divide something so much there comes a point where it can not
be divided any more, that is called atomos or uncuttable.

Dalton (1803) came up with the idea of sub-atomical particles.

In 1922 Dr. Niels Bohr organized the model of the atom by putting the electrons on the outside
and the nucleus in the middle. We still use Bohr's basic model of the atom today.

In 1926 Werner Heisenberg proposed regions called orbits that state where electrons are most
likely to be; this is like the darts we threw that went randomly to new spots, just like electrons move to random spots.
Also, electrons are most likely to be found toward the nucleus of the atom and have an average of two electrons in
the first shell (area), eight electrons on the average in the next shell are and so forth.

Parts of the atom:

The atom is	the smallest whole particle that can exist and still be what it is. It has three common parts called electrons, neutrons and protons.
I. Protons have	positive charges and are found in the nucleus of the atom. This is the also the atomic number.
II. Neutrons have	neutral charges and are also found in the nucleus of the atom.
III. Electrons have	negative charges and are found in the shells/orbits of the atom. There can only be 2 electrons in the first shell, eight electrons in the second shell, 18 electrons in the third shell, and up to 32 electrons in the fourth, fifth and sixth shells.
If you change the number of protons	you change the element or atom. Example * Adding one proton to hydrogen would make it helium.
Changing the number of neutrons	will make it an isotope of that element (Example: Different types of carbon, 12, 13, 14, & 15.).

Periodic Table Information

Helium

4.0

The atomic symbol is	a CAPITAL letter usually followed by a lower case letter. It is chemical shorthand. Ex. "He" is the chemical symbol for helium as shown above.
The atomic mass is	the mass of the atom; the big number (4) shown above.
The atomic number is	the order in which the element is found and the number of protons or electrons in an element. The atomic number for helium is 2 shown above.
A group of elements	is the vertical column of elements found on the periodic table. Examples would be the +1, +2, +3, 4, -3, -2, -1, and 0 or nerd elements.
Demetri Mendeleev, a math guy from Russia,	organized the elements into the periodic table by families.
The periodic table is arranged by	atomic numbers.

Miscellaneous:
Hydrogen is by far the most	abundant and lightest element in the universe.
Isotopes are	atoms with different atomic masses. Example: Carbon 12, Carbon 13, Carbon 14, etc.
An endothermic reaction is	the taking in of heat during a chemical reaction (like an ice pack).
An exothermic reaction	gives off heat during a chemical reaction (like a fire).
Particle size and temperature	can effect reaction rates. Same material, different reaction rates. Small particles will react faster than larger particles.
Light can be given off during a chemical reaction when	electrons jump down in energy levels.
Matter can be changed by	chemical reactions.
Chemical reactions	form new compounds.

Properties of Matter:
Physical properties are	clues that describe what the object is like: color, dull, sharp, hot, shape or the state of matter. Melting is a physical change, not a chemical change.
Chemical properties are	clues that describe how the chemical reaction has take place like: smoking, bubbles, sizzling, light, or heat given off. Some chemical reactions take years to take place (like rust) and others may take a split second.

Parts of a Chemical Equation

2H₂ + O₂--> 2H₂O
Reactants Yields Product (s)

In 2H_3, the number two in front of the "H" is a

coefficient and may be changed when balancing a chemical equation.

In 2H_3, the number three behind the "H" is a

subscript and may not be changed when balancing a chemical equation.

In 2H₃ there are six atoms of

hydrogen.

The reactants are the elements in a

chemical equation that react to form a new substance(s).

A yields sign is an arrow that shows the

direction of the reaction.

The product(s) are the elements in a chemical equation that form

new substance(s).

pH Scale

1	2	3	4	5	6	7	8	9	10	11	12	13	14
Strongest Acid					Weakest Acid	Neutral Salt	Weakest Base						Strongest Base

Mixing a strong acid, like Hydrochloric Acid, and a strong base, like Sodium Hydroxide,	may form a neutral salt-water solution.
A each number away from pH 7	increases the strength by a factor of ten. So a pH of 6 is ten times stronger than a pH of 7, and a pH of 5 is 100 times stronger than a pH of 7....
The pH Scale has a range of 1 to	14.
The pH levels below 7 are	acids.

The pH levels above 7 are bases.

Indicators
Indicators aid in determining	if something is acid or base by changing colors.
Examples of indicators include	red cabbage juice, phenolphthalein, universal indicator and good old pH paper.

Bonding
Reaction rates may be speed up because	smaller particles (increased surface area) like the sawdust burning faster than the 2 x 4 board.
A chemical bond is	a bond that holds chemicals together. Some bonds are stronger than others.
During bonding two or more elements exchange	electrons until they fill their outer shells and become filled to the 2, 8, 18, 32 levels.
H₂O is an example of hydrogen bonded to	oxygen.

Atoms exchange/share

electrons until they fill their outer shells (Bonding).

The negative atoms are attracted to

the positive atoms.

H₂O is an example of two hydrogen atoms bonded to

one oxygen atom.