1. Warm Up
Describe how the periodic table is arranged.

2. The Periodic Table: Organizing the Elements
Chapter 6

3. Dobereiner’s Triad (1829)
Organized the elements into groups of three (triads) according to similar properties.
Example: Halogen Triad – Chlorine, Bromine, & Iodine
React easily with metals.
Atomic mass of bromine is approximately halfway between the atomic masses of chlorine and iodine.
PROBLEM: Not all known elements could be grouped into triads. (Iron, Manganese, Nickel, Cobalt, etc.)

4. Mendeleev’s Periodic Table (1869)
Dmitri Mendeleev, Russian chemist
Organized ~60 elements by INCREASING ATOMIC MASS.
Elements arranged in groups according to repeating properties.
Predicted properties of undiscovered elements.
Mendeleev is credited with the creation of the Periodic Table.

5. Mendeleev’s Periodicity of Elements

6. Mendeleev’s First Periodic Table of Elements

7. Mendeleev’s Periodic Table of Elements

8. Moseley’s Periodic Table (1913) The Modern Periodic Table
Organized by INCREASING ATOMIC NUMBER.
Differences from Mendeleev:
Argon & Potassium
Cobalt & Nickel
Tellurium & Iodine
Elements in vertical columns have similar properties.
PERIODIC LAW: Physical and chemical properties of elements repeat in a regular pattern when they are arranged in order of increasing atomic number.

9. Understanding the Periodic Table
Vertical Columns: Groups or Families
Horizontal Rows: Periods
Divided into three main categories:
Metals: Left Side
Nonmetals: Right Side
Metalloids (Semi-Metals): Along Zig-Zag Line

10. Metals Left of zig-zag line Properties:
Excellent conductors of heat and electricity
High luster (shiny)
All are solids at room temperature (except Mercury)
Many are malleable & ductile.
Malleable: can be hammered into a sheet
Ductile: can be drawn into a wire
Valence electrons:
Most have 1, 2, or 3
Held loosely (LOSE electrons to form compounds).

11. Metals Transition & Inner Transition elements are metals
Inner Transition Elements located below the table
Lanthanides – Rare Earth Elements
Actinides – All are Radioactive & those beyond Uranium are not found in nature.

12. Nonmetals Right of zig-zag line Properties:
Many are gases at room temperature. Those that are solid at room temp. lack luster.
Carbon & Phosphorus - solids
Bromine & Iodine – liquids
Poor conductors of heat and electric current.
Brittle
Valence electrons:
Most have 5, 6, 7, or 8
Held tightly (GAIN or SHARE electrons to form compounds).

13. Metalloids (Semi-metals)
Along the zig-zag line (except Aluminum)
Properties of both metals & nonmetals.
Some are Semiconductors: silicon, germanium, arsenic
Silicon is generally a poor conductor of electricity.
If a small amount of Boron is mixed in the silicon (doping), the mixture is a good conductor. (Used to make computer chips).

14. Metals – Green
Nonmetals – Orange
Metalloids - Purple

15. Key Vocabulary Valence Electrons: electrons in the outer energy level
Atom: neutral (same number of protons & electrons)
Ion: charged atom; has lost or gained electrons
CATION: positive ion formed when electrons are lost.
ANION: negative ion formed when electrons are gained.
Oxidation Number: the charge of the ion created when an element reacts in a chemical reaction (losing/gaining electrons)
Octet Rule: Atoms are stable with 8 electrons in their outer energy level (except Helium)
Atoms are stable if their “s” & “p” sublevels are full.

16. Valence Electrons & Charges
Valence e-’s Charge
Group 1 (IA) (alkali metals)
Group 2 (IIA) (alkaline earth metals)
Groups 3-12 (transition metals) We are going to skip because they can change!
Group 13 (IIIA) (boron group)
Group 14 (IVA) (carbon group) 4 ±4
Group 15 (VA) (nitrogen group)
Group 16 (VIA) (chalcogens)
Group 17 (VIIA) (halogens)
Group 18 (VIIIA) (noble gases) 8 (He – 2) 0

17. Classifying the Elements

18. Classifying the Elements
Periodic Table Groups
Group 1 (1A)
Alkali Metals
Most reactive metal group
Most reactive element: Francium
Never found uncombined in nature
1 valence electron
Loses 1 electron to form compounds
Oxidation number: 1+

19. Classifying the Elements
Periodic Table Groups
Group 2 (IIA)
Alkaline Earth Metals
Very reactive metals
2 valence electrons
Loses 2 electrons to form compounds
Oxidation number: 2+

20. Classifying the Elements
Periodic Table Groups
Group 3-12 (B groups)
Transition Elements & Inner Transition Elements
Variable number of valence electrons & oxidation numbers

21. Classifying the Elements
Periodic Table Groups
Group 13 (IIIA)
Boron Family
3 valence electrons
Shares 3 electrons to form compounds
Oxidation number: 3+

22. Classifying the Elements
Periodic Table Groups
Group 14 (IVA)
Carbon Family
4 valence electrons
Shares 4 electrons to form compounds
Oxidation number: 4±

23. Classifying the Elements
Periodic Table Groups
Group 15 (VA)
Nitrogen Family
5 valence electrons
Gains 3 electrons to form compounds
Oxidation number: 3-

24. Classifying the Elements
Periodic Table Groups
Group 16 (V1A)
Oxygen Family
6 valence electrons
Gains 2 electrons to form compounds
Oxidation number: 2-

25. Classifying the Elements
Periodic Table Groups
Group 17 (VIIA)
Halogens
Form salts when combined with alkali metals
Most reactive nonmetal group
Most reactive: Fluorine
7 valence electrons
Gains 1 electron to form compounds
Oxidation number: 1-

26. Classifying the Elements
Periodic Table Groups
Group 18 (VIIIA)
Nobel Gases
Nonreactive (Inert) Gases
Rarely react in chemical reactions
s & p sublevels of outer energy level is completely filled
8 valence electrons
Exception: Helium – 2 valence electrons
Oxidation number: 0