1. The Periodic Table- Topic 5
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2. Click on pix for history
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3. A. Dmitri Mendeleev (1869, Russian)
I. HISTORY
A. Dmitri Mendeleev (1869, Russian)
Organized elements by
increasing ATOMIC MASS.
Elements with similar chemical properties were grouped together.
There were some discrepancies.
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B. Henry Moseley
ORGANIZED ELEMENTS BY INCREASING ATOMIC NUMBER.
Resolved discrepancies in Mendeleev’s arrangement.
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When elements are arranged in order of INCREASING ATOMIC #, elements with similar chemical properties appear at regular intervals.
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II. ORGANIZATION OF THE ELEMENTS
A. Arrangement of Table
1. Horizontal rows
Called PERIODS
All elements in the same period have the same number of ENERGY LEVELS in their atomic structure
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2. Vertical Columns
Called GROUPS OR FAMILIES
All elements in the same group have the
same number of VALENCE ELECTRONS, therefore lose or gain the SAME number of electrons, form similar CHEMICAL FORMULAS and have similar CHEMICAL PROPERTIES
ex. XCl Group 2:
Be +2 Cl -1 = BeCl2
Mg +2 Cl = MgCl2
Remember: When writing formulas, use the criss-cross rule to cancel out oxidation states
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8. III. Comparing Metals, Nonmetals & Metalloids
Elements on the Periodic Table are divided into three subgroups called METALS, NONMETALS and METALLOIDS (semimetals).
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Increase metallic properties
Increase nonmetallic properties
Decrease metallic properties
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METALS: located on the LEFT SIDE of the periodic table (except H); MORE THAN 2/3 of all elements
1. Chemical properties
tend to LOSE ELECTRONS EASILY
have LOW IONIZATION ENERGY (energy needed to remove electrons)
Metallic character INCREASES as ionization energy decreases.
have LOW ELECTRON AFFINITY (attraction for electrons)
form POSITIVE IONS when combining with other atoms
FRANCIUM most reactive metal: See Table J
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10. 2. Metals Physical Properties
good conductors of heat and electricity
LUSTROUS - reflect light, shine when they are polished
MALLEABLE - can be rolled or hammered into sheets
DUCTILE - can be drawn into wires
are SOLIDS at room temperature except for MERCURY (liquid)
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B. NONMETALS
located on the right side of the periodic table (except for Noble gases)
Chemical properties
tend to GAIN electrons to form NEGATIVE IONS
have high electron affinities (electronegativity)
produce COVALENT bonds by SHARING electrons with other nonmetals
FLUORINE most reactive nonmetal: see Table J
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2. Nonmetals Physical Properties
exist as gases, molecular solids, or network solids at room temperature except BROMINE (liquid)
BRITTLE - (shatters when struck)
DULL - does not reflect light even when polished
POOR CONDUCTORS of heat and electricity
Allotropes: Different SHAPE & PROPERTIES forms from the same element.
CARBON: coal; diamond, graphite
OXYGEN: O2; O3 (OZONE)
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C. METALLOIDS
Found lying on the jagged line between metals and nonmetals flatly touching the line (except Al and Po).
B,Si,Ge,As,Sb,Te & At
Exhibit properties of both metals and nonmetals
Behave as nonmetals but their conductivity is like metals
SEMICONDUCTORS – Si and Ge
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IV. Periodic Trends – use Table S
A. Periodic Law
When elements are arranged in order of increasing atomic #, elements with similar properties appear at regular intervals.
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15. 1) Ionization Energy
Energy needed to remove the most loosely bound electron from a neutral gaseous atom
X + energy X+ + e-

16. Trends in Ionization Energy
6.3
Trends in Ionization Energy
First ionization energy tends to increase from left to right across a period and decrease from top to bottom within a group. Predicting Which element would have the larger first ionization energy—an alkali metal in period 2 or an alkali metal in period 4?

17. Trends in Ionization Energy
IE increases as you move across a period
Why?
The nuclear charge (atomic #) is increasing therefore greater attraction of the nucleus for electrons hence harder to remove an electron

18. Trends in Ionization Energy
IE decreases as you move down a group
Why?
Atom size increases making the outermost electron farther away from the nucleus therefore making it easier to remove
Shielding increases

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© 1998 LOGAL
2. Atomic Radius
½ the distance between nuclei
Decreases to the LEFT and Increases as you go DOWN
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Atomic Radius cont.
Why is it larger going down?
Higher energy levels have larger orbitals
Shielding - core e- block the attraction between the nucleus and the valence e-
Why is it smaller to the right?
Increased nuclear charge without additional shielding pulls e- in tighter
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Comparison???
Why is the ionization energy opposite that of atomic radius?
In small atoms, e- are close to the nucleus where the attraction is stronger
Why small jumps within each group?
Stable e- configurations don’t want to
lose e-
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3. Electronegativity
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the ability for an atom to attract electrons (electron affinity)
Based on a scale of 4, Fluorine having the greatest EN
A. Metals
lose e-
Form Cations (+)
get smaller
B. Nonmetals
gain e-
Form Anions (–)
Get larger
© 2002 Prentice-Hall, Inc.
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23. Trends in Electronegativity
6.3
Trends in Electronegativity
Representative Elements in Groups 1A through 7A

24. 4. Melting/Boiling Point – Table S
Highest in the middle of a period.
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25. Periodic Trends Summary (use reference Table S for data comparison)
Across a period (L to R)
Down a group
Ionization energy
increases
decreases
Electronegativity
Atomic radii
Metallic properties
Click on for video clip 4:41
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IV. Classification
Alkali Metals
Alkaline Earth Metals
Transition Metals
Halogens
Noble Gases
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Group 1: Alkali Metals
extremely reactive (not found free in nature)
form stable ionic compounds
react with water to form a base
react with air to form oxides
react with acids to form salts
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28. Group 2: Alkaline Earth Metals
reactive (not found free in nature) - form stable ionic compounds
react with water to form a base
react with air to form oxides
react with acids to form salts
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29. Groups 3-11: Transition Metals
multiple positive oxidation states
Lose electrons from two outermost energy levels
Ions form colored solutions
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30. Group 15 – unique features
Members range from typical nonmetals (nitrogen and phosphorus) through metalloids (arsenic and antimony) to metals (bismuth)
Nitrogen
Forms stable diatomic molecules with a triple bond
Component of protein
Forms some unstable compounds that are used as explosives
Phosphorus
Component of nucleic acids (DNA, RNA)
More reactive than nitrogen at room temperature
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31. Group 16 – unique Features
Members range from typical nonmetals (oxygen and sulfur) through metalloids (selenium and tellurium) to metals (polonium)
Solids except oxygen
Oxygen can exist as O2 and O3 (it is an allotrope)
Polonium is radioactive
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Group 17: Halogens
very reactive nonmetals - high electronegativity
not found free in nature
form diatomic molecules when free
react with metals to form salts (halides)
Found in all three phases (s, l, g) due to differences in Van der Waals forces (these are weak)
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Group 18: Noble Gases
Have complete outer shells
Almost inert (not reactive); stable
Krypton, xenon, and radon form compounds with oxygen and fluorine
Referred to as monatomic gases
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