Download Atomic Theory Outline

I. The Atom - smallest piece of matter that still retains properties of the element
a. The Nucleus
i. Protons
1. Positive charge (1+)
2. Made of 3 quarks
3. Mass of 1 amu each (same as neutron)
ii. Neutrons
1. Neutral (no/0) charge
2. Made of 3 quarks
3. Mass of 1 amu (same as proton)
b. Electrons
i. Negative charge (1-)
ii. In a cloud around the nucleus – moving quickly so we imagine it to be blurry like the blades
of a fan. Cloud makes up most of the volume of the atom, but is mostly empty space.
iii. Cloud is made of shells, based on different energy levels of electrons
iv. Very low mass compared to N and P. (1800 electrons = mass of one proton)
II.
Symbols
i. One or two letter representation of an element
ii. First letter capital, second (if there is one) is lower case.
iii. Usually come from English, Latin, or Greek names of the element.
III.
Elements and Numbers
a. Mass Number
i. Number of protons + number of neutrons
ii. Unit is the amu – atomic mass unit
b. Atomic Number
i. Equal to the number of protons in the atom
ii. This is the number that identifies an atom as a particular element
IV.
Isotopes
a. Different versions of atoms based on different numbers of neutrons.
b. Different isotopes have different properties.
c. Average Atomic Mass
i. Weighted average of the mass of all the different isotopes (versions) of an element
ii. Usually we can round this to the closest whole number to find the most common isotope.
d. Name of element followed by mass number identifies isotope. i. e. Carbon-12 is a a carbon atom
with mass of 12 amu.
e. Atomic mass – atomic number = number of neutrons
V.
Periodic Table
a. Originally created by Dmitri Mendeleev in late 1800s – organized by increasing atomic mass
b. Adjusted by Henry G.J. Moseley to be in order of increasing atomic number instead.
c. Columns
i. Called groups or families, labeled by number (1-18)
ii. Each family has the same number of electrons in their outer most shell, called the valence
shell or valence electrons.
iii. Elements in the same group will react in similar ways because of the number of valence
electrons.
d. Rows
i. Called periods
ii. Elements in the same period have the same number of electron shells
e. Electron Shells
i. Divisions of the electron cloud based on different energy levels
ii. Each shell can hold a number of electrons equal to 2n2, where n = the number of the level.
iii. Lower level shells are closer to the nucleus and have less energy.
iv. Electrons must fill in closer, low energy shells
before the further, high energy shells can be
filled.
v. The goal of all atoms is to have a full valence
shell. Atoms will borrow, give, or steal
electrons to do this.
vi. The “magic” number of electrons in the outer
level is 8. This is called the octet rule.
vii. This example to the right is sodium,
identifiable because its 11 electrons.
f. Regions
i. Everything to the left of, but not touching, the stair-step line on the PToE are metals.
Exceptions: H is a nonmetal. Al is a metal.
ii. Everything to the right of, but not touching, the stair-step line on the PToE are nonmetals.
Exceptions: H is a nonmetal
iii. Everything touching the stair-step line is a metalloid. These have some properties of metals
and some properties of nonmetals. Exception: Al is touching the line, but is a metal.
VI.
Electron Dot Diagrams
a. Created by a college chemistry teacher named G.N. Lewis.
b. Made by taking the symbol of the element and surrounding it with the correct number of valence
electrons.
c.