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I II III
Unit XI: Periodic Properties
I. History(p. 123 - 127)
A. Mendeleev
Dmitri Mendeleev (1869, Russian)
Elements were put in order of increasing atomic mass.
Elements with similar properties were grouped in columns.
• In some places, masses don’t go in order to complete the pattern. These elements were still assigned to the column their properties matched. (On the assumption that there must be errors in their masses.)
A. Mendeleev
Mendeleev’s table was a major breakthrough because it could predict element properties.
Mendeleev left gaps in locations where no known element had the necessary properties to fit the pattern.
Based on the patterns he’d identified, he predicted properties of three of the “missing” elements.
A. Mendeleev
Mendeleev’s predicted
elements were later
discovered/identified and were found
to have the properties he’d predicted.
B. Moseley
Henry Moseley (1913, British)
(Built on Bohr’s principles of
emission spectroscopy)
Used x-ray spectrometry to determine the number of protons in each element.
This generated the values we now call “atomic number.” (These were not known in Mendeleev’s time.)
B. Moseley
Organized elements in the periodic table by increasing atomic number.
This resolved the mass discrepancies in Mendeleev’s arrangement.
The Modern Periodic Law:
When elements are ordered by atomic number, chemical and physical properties recur periodically.
B. Moseley
The Modern Periodic Law is sometimes stated:
The properties of the elements are periodic function of their atomic numbers.
Graphing by atomic
number shows
repetitive patterns in
element properties.
I II III
I. Periodic Table Vocabulary
Ch. 5 - The Periodic Table
B. Blocks
s pd
f
Main Group ElementsTransition Metals (d-
block)Inner Transition Metals
(f-block)
B. Blocks
A group or “family” is a column on the periodic table, e.g., the alkali metals or the noble gases.
B. Groups
A period is a row on the periodic table– all the way across, regardless of block.
B. Groups
Period 6 includes 6s, 5d, 6p
and 4f
Period 4:
4s, 3d, 4p
I II III
II. Organization of theElements
Ch. 5 - The Periodic Table
MetalsNonmetalsMetalloids
A. Metallic Character
Alkali metalsAlkaline earth metalsTransition metalsLanthanidesActinides
Periodic Table SectionsOther metalsMetalloidsOther nonmetalsHalogensNoble Gases
Elements within a GROUP have similar properties
Because they have similar electron arrangements.
Periodic Table Sections
1s1
2s1
3s1
4s1
5s1
6s1
7s1
Periodic = every so oftenWhen elements are arranged in order of
atomic number, elements with certain properties recur periodically.
The Periodic Table
There is a predictable pattern. It repeats for each PERIOD.
The Periodic Table
Period 3
Na
Mg
AlSiPSCl
Ar
In a PERIOD, atomic radius decreases as atomic number increases.
Atomic Radius
Group 1
H
LiNa
K
RbCs In a
GROUP, atomic radius increases as atomic number increases.
Ionization Energy
Period 3
Na
Mg
Al
Si
PS
ClAr
In a PERIOD, ionization energy increases as atomic number increases. (But not smoothly.)
Atomic Radius
Group 1
H
LiNa K Rb Cs
In a GROUP, ionization energy decreases as atomic number increases.Fr