1. Unit 3 – Lesson 1
Periodic Table

2. Periodic Table Development
Lesson 1
Periodic Table Development
There are 109 individual squares, each showing the element name, element symbol, atomic number and atomic mass. Some tables show more information.

3. Dmitri Mendeleev
In 1869 he published a table of the elements organized by increasing atomic mass.

4. Henry Moseley
In 1913, through his work with X-rays, he determined the actual nuclear charge (atomic number) of the elements. He rearranged the elements in order of increasing atomic number.
Henry worked with Ernest Rutherford at his lab.
By sorting by positive charge instead of by atomic number, the property/mass problems all worked out.

5. Glenn T. Seaborg
After co-discovering 10 new elements, in 1944 he moved 14 elements out of the main body of the periodic table to their current location below the Lanthanide series. These became known as the Actinide series.

6. Periodic Law
When elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties.

7. The horizontal rows are called PERIODS.
Each period represents elements with the same number of shells and with one more shell than the period before it.

8. The vertical columns are called GROUPS or FAMILIES.
Elements in a family have the same number of valence(outer shell) electrons. Hydrogen is really in a group by itself.
The vertical columns are called GROUPS or FAMILIES.

9. Semimetals(Metalloids)-middle
Metals-left side
Luster, conductors, malleable, ductile, solids
Positive ions
Nonmetals- right side
Dull, insulators, shatter, brittle
Negative ions
Semimetals(Metalloids)-middle
intermediate characteristics
Elements touching black “stair-step” line (except Aluminum which is a metal)

10. Ions 
To become stable, atoms gain or lose electrons to fill their outermost energy level (valence shell) with 8 electrons (Octet rule).
Metals lose electrons to achieve eight electrons in their valence shell.
Nonmetals gain electrons to achieve eight electrons in their valence shell.

11. Examples What is the electron configuration of Oxygen?
1s2 2s2 2p4
There are 6 e’s in the n=2 energy level so oxygen will gain two e’s to make 8, leaving O-2
What is the electron configuration of Mg?
1s2 2s2 2p6 3s2
Mg will lose the 2 n=3 electrons and therefore have 8 valence electrons as Mg+2

12. Alkali Metals (Group 1) 1 valence electron Form 1+ ions
Found in compounds in nature, very rarely found as pure elements
Most reactive metals (explaining above)
These were first found in ashes.
Properties: soft shiny solids, low density, low melting points, reacts easily with oxygen and group 17.
Sodium and potassium are the most abundant, about 3% of ocean by mass.
Sodium is produced by passing electricity through table salt.
Alkali Metals Demo
Sodium
Lithium
Potassium
See attached.

13. Hydrogen Nonmetal 1 valence electron Forms 1+ or 1- ions
Most common element in the universe. Most of it found on earth is in water.
Elemental hydrogen can escape earth’s gravity so not much of it is around.
Acid/base chemistry is bases on the presents of absence of the hydrogen ion.

14. Alkaline Earth Metals (Group 2)
2 valence electrons
Form 2+ ions
Found in compounds in nature, rarely found as pure elements
Not as reactive as the Alkali Metals but still quite reactive
These have a higher density and melting point than the Alkali metals.
They are used mostly for alloys.
Beryllium is strong as steel but much lighter.
Found in: antacids, limestone, chalk, marble

15. Boron Family (Group 13 or 3A)
3 valence electrons
Contains a metalloid (boron) and metals
These are relatively noncorrosive
Aluminum ore comes from bauxite ore and is very common

16. Carbon Family (Group 14 or 4A)
4 valence electrons
Contain non-metals, metalloids, and metals
CARBON
Found in almost everything
Basis of organic chemistry
SILICON
2nd most abundant element
Found in sand glass transistors and solar cells

17. Nitrogen Family (Group 15 or 5A)
5 valence electrons
Has nonmetals, metalloids, and metals
NITROGEN
80% of the atmosphere is nitrogen
Plants can’t remove nitrogen from the air, they must get their nitrogen from the soil
Ammonia is produced in large quantities as a fertilizer.
PHOSPHEROUS
Needed for strong bones and teeth
Also found in fertilizers, detergents, and sour flavors.

18. Oxygen Family (Group 16 or 6A)
6 valence electrons
Contains nonmetals, metalloids and a radioactive element (Po)
OXYGEN
Most abundant element on earth
Combustion is always a reaction with oxygen
Ozone (O3) is air pollution
SULFUR
Also called brimstone and fool’s gold
Typically an unpleasant odor
Most used to make sulfuric acid

19. Halogens (Group 17 or 7A) 7 valence electrons Form 1- ions
Found in compounds in nature
Very reactive
Astatine is radioactive
Most of these are very colorful.
FLOURINE
Most reactive and very corrosive.
Chlorofluorocarbons (CFC) are linked to the ozone depletion
CHLORINE
This is the most useful of the halogens
Used in disinfectants, salt, PVC pipes and more
The others are used in flame retardents, pesticides, photo film

20. Noble Gases (Group 18 or 8A)
8 valence electrons with the notable exception of helium. Helium has two.
Most are non-reactive.
All are gases.
Argon is the most abundant.
The biggest noble gases can be forced to react under the right conditions.

21. Representative vs Transition Elements
Representative (main group or A groups) are groups 1, 2, 13 – 18
Transition (B groups) elements are groups