1. Science AHSGE II-3
The Periodic Table

2. The Periodic Table
Element- Any substance that can not be broken down into simpler forms
Listed in squares w/basic items:
Atomic number- # of protons (electrons as well- in a neutral atom); the smaller number
Atomic Mass (Weight)- # of protons and neutrons in an atom; the larger number (sometimes a decimal)
Neutrons= atomic mass – atomic number
Atomic symbol- Letter(s) used to identify element
Dmitri Mendeleev- First arranged by increasing atomic weight
Henry Moseley- Correctly arranged by increasing atomic number

3. Atoms The simplest substances on Earth
Nucleus- Center containing protons (positive charge) and neutrons (no charge)
Electron cloud- Area surrounding nucleus where electrons (negative charge) are found in energy/electron levels/shells/orbits

4. The Periodic Table Horizontal rows= Periods (7)
Share the same number of electron levels
Reactivity decreases as you move left to right across a period
Vertical columns= Groups or families (18)
Share common physical and chemical characteristics
Same number of valence electrons (electrons in the outermost level)
HINT: The roman numeral in front of the A
Reactivity increases as you go down the column
Hydrogen does not belong to any family

5. The Periodic Table 3 main groups of elements:
Metals- On the left and middle of periodic table
High hardness- Resists scratching
Highly conductive- Allows for energy transfer
Have luster- shiny
Metalloids- Along the zig-zag line
Characteristics of metals and nonmetals
Non-metals- On the right side
Brittle solids or gases
Low conductivity
No luster

6. Families IA- Alkali metals; one valence electron
IIA- Alkaline Earth Metals; two valence electrons
IIIB- IIB – Transition Metals
IIIA- Boron group; three valence electrons
IVA- Carbon group; four valence electrons
VA- Nitrogen group; five valence electrons
VIA- Oxygen group/Chalcogens; six valence electrons
VIIA- Halogens/Halides; seven valence electrons
VIIIA- Noble Gases; eight valence electrons

7. The Bohr Diagram
A diagram of all electron shells in the electron cloud
The first electron shell holds two electrons
All other electron shells hold eight electrons
Try these:
Lithium
Chlorine
Krypton
Nitrogen
Which one of these does not work?

8. Lewis Dot Structure
Diagram representing the valence electrons of an element
Atomic symbol surrounded by dots on four sides
Eight valence electrons total
Put one dot per side and then double up
Try these:
Xenon
Cesium
Gallium
Nitrogen

9. The Octet Rule and Ions
All atoms, except for hydrogen and helium, require eight electrons in the outermost shell to become stable
Noble gases are not reactive; already stable
Ions- Atoms whose valence electrons have been gained or lost to reach this stability (charged particle)
Gain electrons to reach eight- negative charge
Lose electrons to drop back to shell behind that is already full- positive charge

10. Octet Examples
Give the ionic charge for each of the following: (write the symbol with the charge)
Phosphorous
Potassium
Tellurium
Magnesium
Oxygen