1. The Periodic Table Until 1750 only 17 known elements Mainly metals
-such as copper and iron

2. The Periodic Table
In 1789 A French Chemist Lavoiser grouped known elements into groups he called metals, non-metals, gases and earths

3. Dmitri Mendeleev Dmitri Mendeleev (1869, Russian)
Organized elements by increasing atomic mass.
Predicted the existence of undiscovered elements.

4. Mendeleev Periodic Table
In 1860 there were 63 known elements
Needed a way to organize them to teach his students
Inspired by the card game, “solitaire”

5. Mendeleev Proposal
On each card he listed the elements name, mass, and properties
Arranged the elements into rows in order of increasing mass
In a column the masses increased from top to bottom

6. Mendeleev’s Prediction
Could not make a complete table of the elements (many still undiscovered)
Left spaces in his table for those elements

7. Evidence Mendeleev predicted a soft metal with a low melting point
In 1875 French chemist discovered Gallium (melting point 24.7 degrees Celsius)
Showed how useful the periodic table could be

8. Henry Mosely Henry Mosely (1913, British)
Organized elements by increasing atomic number.
Fixed problems in Mendeleev’s arrangement.

9. The Periodic Table
Metals
Nonmetals
Metalloids

10. Columns & Rows
Group (Family), Vertical
Period, Horizontal

11. Periods Each row in the table of elements is a period
Period 1 has 2 elements, periods 2-3 has 8 elements, periods 4-5 has 18 elements, and period 6 has 32 elements

12. Groups Each column on the periodic table is called a group
Elements within a group have similar properties
Elements of a group have similar electron configurations and chemical properties

13. The Periodic Table Periodic Law
Properties of elements repeat periodically when the elements are arranged by increasing atomic number.

14. Periodic Table Atomic Mass:
-is a value that depends on the distribution of an elements isotopes in nature and the masses of those isotopes
-Protons plus Neutrons

15. Periodic Table Atomic Mass Units (amu)
-Is defined as 1 / 12 the mass of a carbon – 12 atom

16. Classes of Elements 3 ways to classify elements
-classified as solids, liquids, and gases
-those that occur naturally in nature and those that do not

17. Classes of Elements
-Puts elements into categories based on their general properties
-metals, nonmetals, and metalloids

18. Metals Majority of elements are metals
Good conductors of heat and electric current
Most metals are malleable (ability to be hammered)
Some reactive with other elements some do not

19. Nonmetals Properties opposite of metals
Poor conductors of heat and electricity
Low boiling points, usually gases at room temperature

20. Metalloids
Elements with properties that fall between metals and nonmetals
-EX: Graphite

21. Variation Across a Period
Across the periodic table from left to right, the elements become less metallic and more nonmetallic in their properties

22. Periodic Table Valence Electrons e- in the outermost energy level
Highest occupied energy level
Properties vary across a period, because the # of valence electrons increases from right to left

23. Valence Electrons Plays a key role in chemical reactions
Elements in a group (up/down) have similar properties, because they have the same number of valence electrons

24. Alkali Metals Elements in group 1A are called alkali metals
Only have 1 valence electron and are extremely reactive
Found in nature as compounds
-EX: table salt, compound of sodium / chlorine

25. Alkaline Earth Metals Group 2A has 2 valence electrons
Differences in reactivity with Alkaline Earth Metals are shown by the ways they react with water

26. Examples of Alkaline Earth Metals
Magnesium – plays a key role in the process the uses sunlight to produce sugar in plants
Calcium – your body needs calcium to keep your bones and teeth strong

27. The Boron Family
Group 3A contains the metalloid boron and 4 metals (3 valence electrons)
Most abundant metal in the earth’s crust is aluminum
-Strong, light weight, malleable, and a good conductor of heat / electricity

28. The Carbon Family Group 4A contain 4 valence electrons
Life on earth would not exist without carbon
Except for water, most of the compounds in your body contain carbon

29. The Nitrogen Family
Group 5A includes elements with a wide range of physical properties
Have 5 valence electrons
Nitrogen and phosphorus are the most important elements in group 5A

30. The Oxygen Family
Group 6A has 3 nonmetals and 2 metalloids (6 valence electrons)
Oxygen is the most abundant element in the earth’s crust
Complex life forms need Oxygen to stay alive
-Oxygen is used by the body to release the energy stored in food

31. The Halogens Elements in group 7A are called Halogens
Has 7 valence electrons
Despite their physical differences, they have similar chemical properties

32. The Noble Gases Elements in group 8A are called noble gases
Helium has 2 valence electrons where the other noble gases has 8
Noble gases are colorless and odorless and extremely un-reactive

33. Periodic Trends Group # = # of valence e- (except He)
Families have similar reactivity.
Period # = # of energy levels 1A 2A
3A 4A 5A 6A 7A 8A

34. Dot Diagrams
Dots represent the valence e-.
EX: Sodium
EX: Chlorine