1. ORGANIZING THE ELEMENTS
Section 16-1

2. Why is the PERIODIC Table important?
Periodic – regular, repeating pattern.
Days of the year are organized on a calendar.
Periodic table is the most useful tool to a chemist.
It organizes lots of information about all the known elements.
You get to use it on most tests.

3. Pre-Periodic Table Chemistry …
…was a mess!!!
No organization of elements.
Imagine going to a grocery store with no organization!!
Difficult to find information.
Chemistry didn’t make sense.
DISCOVER Activity on page 500
Partner activity
4 sets of 10 numbers in various colors

4. Dmitri Mendeleev: 1869 Father of the Periodic Table
HOW HIS WORKED…
Recognized a hidden pattern
Put elements in rows by increasing atomic mass. (average mass of one atom of an element)
Put elements in columns by the way elements reacted or the bonding power.
SOME PROBLEMS…
He left blank spaces for undiscovered elements and predicted their properties. (Turned out he was right!)
He broke the pattern of increasing atomic mass to keep similar reacting elements together.

5. Structure of an Atom

6. The Periodic Table and The ATOM
Electron Cloud or Electron Shell
Outside the nucleus of an atom
Most of the volume of an atom
Negative electrons (1/2000 amu)
Electrons move constantly and rapidly around the nucleus
Nucleus
Tiny core of an atom
Most of the mass of an atom
Positive protons (1 amu)
Neutral neutrons (1 amu)

7. An Atom on the Periodic Table
Atomic Number P or E
Element’s identity (social security number)
Protons (also Electrons) 26 Fe
Iron
55.847
Atomic Symbol
One or two letter symbol
First letter is always capital
Atomic Name
Origins in greek or latin root words
Atomic Mass (P + N)
Protons (unique) + Neutrons (varies)
Average mass of one atom

8. The Modern Periodic Table
Mendeleev wasn’t too far off. The 3 missing elements were discovered within 16 years.
Now the 100+ elements are put in rows by increasing ATOMIC NUMBER!!
The horizontal rows are called periods and are labeled from 1 to 7.
The vertical columns are called groups or families are labeled from 1 to 18.

9. Exploring the Periodic Table

10. Valence Electrons – Why It Works!
Located in the outermost shell
Involved in bonding
HAPPY ATOM is when the outermost shell is full P+ N
1st shell – 2 electrons
2nd shell – 8 electrons
3rd shell – 8 electrons
Load electrons from the inside to the outside shell

11. Valence Electrons – Outermost ShellP+ N

12. The Modern Periodic Table