Download The Periodic Table of Elements Mendeleev

Chapter 7
Periodic Properties of Elements
Burns
FUNDAMENTALS OF CHEMISTRY 4/e
The Periodic Table of Elements
• Elements are organized according to their
physical and chemical properties in the
Periodic Table of the Elements.
Mendeleev
• Father of the Periodic Table (1869)
• Mendeleev’
Mendeleev’s Periodic Law- Both physical and
chemical properties of the elements vary periodically
with increasing atomic mass. (Å slightly flawed)
• Modern Periodic Law: Both physical and
chemical properties of the elements vary
periodically with increasing atomic number
(Required!)
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Periodic Table of the Elements
Lanthanides (rare earth)
Actinides
From Chapter 4
Periods of Elements
• Periods of elements are the horizontal rows
of the Periodic Table.
• The properties of the elements vary as you
move from left to right across the periods.
– Periodicity
Groups
(a.k.a. Families)
• Vertical columns of elements in the periodic table
are called groups.
• Elements in the same group or family have similar
chemical properties.
• Main Group (Representative) Elements are
those in the first two groups and the last six groups
in the periodic table. These groups are designated
IA - VIIIA group elements
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Valence Electrons
(Section 5.4, p. 130)
• Number of valence electrons = group number (Roman)
• The number of valence electrons increases as you move
from left to right across a period.
• The periodic changes in properties (periodicity) parallels
the change in the number of valence electrons.
Periodic Trends
• Atomic Radius (required!)
– Left Æ right within the period: decrease (why?)
– Top Æ bottom within the group: increase (why?)
• Ionic radius (required!)
– Atom Æ anion: increase; atomÆ cation: decrease
– Isoelectronic (?) ions/atom: higher Z, smaller radius
• Ionization Energy (required!)
– Left Æ right within the period: increase
– Top Æ bottom within the group: decrease
– Trends opposite that of atomic radius (why?)
• Melting points and boiling points (self study)
• Density and conductivity (self study)
Survey of Elements by Groups
Sec. 7.7
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Group IA, The Alkali Metals
• Elements are:
– Low ionization potential
– Highly reactive with water, oxygen, other elements
– Na is 6th in abundance. K is 7th in abundance in
earth’s crust.
Group IIA, Alkaline Earth Metals
• The elements:
–
–
–
–
Low IE (but higher than group IA).
Are less reactive than group IA.
Have 2 valence electrons and form 2+ ions.
Calcium is fifth in abundance in the earth’s crust
Group IIIA
• Boron is a metalloid; Others are metals
• Metallic elements form +3 ions.
Organic Boron Chemistry:
Herbert C. Brown (1912-2004)
Nobel Chemistry Laureate, 1979
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Group IVA, The Carbon Family
• Metallic character increases with increasing Z.
• Carbon has several allotropes (forms)
• Carbon ≡ Energy
– Carbohydrates
– Hydrocarbons (petroleum)
– CO2 – greenhouse gas
• Silicon: second most abundant (earth’s crust);
Exist as SiO2 (silica) and silicates
Allotropes of Carbon
Å C60 a.k.a.
Bucky Ball
Allotropes: Forms of an element having different physical properties due to different
atomic arrangements
Group VA
• N2, 78% of air
• Nitrogen in amino acids & nucleic acids.
• N2 & H2 to form ammonia, NH3
• P - Allotropes: red; yellow-white
• Phosphate (PO43-) esters – DNA/RNA
linkers
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Group VIA, The Oxygen Family
(Chalcogens)
Chalcogens)
• Oxygen as O2 gas is essential to life.
– O2 is the oxidizer in combustion and metabolism
– O2 is 21% of the earth’s atmosphere
• Oxygen makes up 49% of the earth’s crust.
• Ozone, O3, is an allotropic form of oxygen.
• Sulfur occurs free in nature as S8
• S used in sulfuric acid (H2SO4) and in making tires
(vulcanization)
Group VIIA, The Halogens
• Halogens contain 7 valence electrons, exist as
diatomic gas.
• Fluorine is a reactive, pale, yellow gas.
• Chlorine is a reactive green
- yellow gas
• Bromine is a red liquid (highly corrosive)
• Iodine is a purple crystalline solid that sublimes
Group VIIIA, Noble Gases
• Mono- atomic gases; 8 valence electrons
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