Download Atoms and the Periodic Table

Chapter 18
Atoms and the Periodic Table
Section 1 (p. 544-549)
Chemical Symbol: Shorthand way to write the name of
the element.
 First letter capital letter
 Second letter lower case
*Memorize Table 1, page 544
Atom: Smallest piece of matter that still has the
properties of the element.
 Made up of Protons, Neutrons and Electrons
Nucleus: Positively charged center of the atom.
 Contains 99.9% of the mass of the atom
 Size = 1/100,000 of the atom (like a golf ball in a
football stadium)
Protons
Found in nucleus
Positive 1 charge
Mass = 1 a.m.u.
Neutrons
Found in nucleus
Neutral (no charge)
Mass = 1 a.m.u.
Electrons:
 Found outside the nucleus
 Negative 1 charge
 Mass 1/1836 a.m.u.
Quarks: Smaller particles that make up protons and
neutrons
Changing Atomic Model: See page 548
 Democritus, 400 B.C.: Atoms make up all
substances
 John Dalton, 1800’s: Proved that atoms exist
 Model of the atom went through many changes
 Electron Cloud Model: Current Model
Electron Cloud Model:
 Electrons do not follow fixed orbits
 Electrons tend to occur more frequently in certain
areas around the nucleus
Electron Cloud: Area around the nucleus where atoms
electrons are most likely to be found
 100,000 x larger than the diameter of nucleus
 Contains different energy levels
Ch. 18, Section 2 (p.550-553)
Atomic Mass Unit (a.m.u.): The measurement used for
atomic particles.
Atomic Number: The number of protons in the nucleus
of an atom.
 Specific for each element!
 Ex: Carbon
atomic number 6 = 6 protons
 Ex: Oxygen
atomic number 8 = 8 protons
 Ex: Sodium atomic number 11 = 11 protons
Mass Number: Sum of the protons and neutrons in the
nucleus of an atom.
# neutrons =
mass # - atomic #
atomic number
atomic mass
Drawing Atoms
1.
Begin by drawing the nucleus. Write in the number
of protons and neutrons in the nucleus.
2.
Place electrons in energy levels (remember
number of electrons = number of protons in a
neutral atom)
3.
Fill in energy levels from inner levels to outer
levels.
4.
First energy level can hold up to 2 electrons.
5.
Second and third energy levels can hold 8
electrons (for our class)