Transcript Periodic Table and Periodicity

Periodic Table and
Periodicity
Dmitri Mendeleev
“The elements, if
arranged
according to their
atomic weights,
exhibit an
apparent
periodicity of
properties.”
I.
History
• A. Dimitri Mendeleev, 1869
• B. Moseley, 1914
– periodic law: The chemical and physical
properties of the elements are periodic
functions of their atomic numbers; When the
elements are arranged in order of increasing
atomic number, there is a periodic repetition
of their properties.
II. Structure/Organization
• A. Periodic table
– Periods
– Groups or families
Valence electrons
- Representative elements
• B. Metals
- Alkali metals
- Alkaline earth metals
- Transition metals
- Inner transition metals
• C. Nonmetals
- Halogens
- Noble gases
• D. Semimetals/metalloids
Compare properties of metals and
nonmetals
III.
Periodicity in properties
• A. Ionization energy
Ionization Potential/Energy
IE: Energy required to remove eHigher the IE: more difficult to remove eAcross Period
IE INCREASES*
* with decrease @ each subshell
Why?
Down Group
IE DECREASES
Why?
• B. Electronegativity
Electronegativity
The ability to attract eAcross Period
EN INCREASES
Because nuclear charge (# p+) increases
Down Group
EN DECREASES
Because more n, more shielding, efurther away
from nucleus
•C. Atomic/ionic radius
Atomic Radius
Across Period
Atomic size DECREASES
Because nuclear charge (# p+) increases,
as e- are added to same n, pulls e- in tighter
Down Group
Atomic size INCREASES
Because more n (shells), more shielding,
e- further away from nucleus
Ionic
Ionic Radius
IonCharged atom
Cation
Positive (+) ion (neutral atom looses e-)
Anion
Negative (-) ion (neutral atom gains e-)
Ionic Radius
Across Period
IR DECREASES*
* with jump up in size @ metalloids
Down Group
IR INCREASES
Compare to neutral atom Ex. Br
Valence e- are the outermost e- of an atom
D.
Metallic character/nonmetallic
character
Nonmetallic character
increases
Metallic
Character
Increases
Metallic Properties
Across Period
MP DECREASES
Down Group
MP INCREASES
Summary of Periodic Table
Trends
•
•
•
•
•
Moving Left --> Right
Atomic Radius Decreases
Ionization Energy Increases
Electronegativity Increases
Metallic character decreases
•
•
•
•
•
Moving Top --> Bottom
Atomic Radius Increases
Ionization Energy Decreases
Electronegativity Decreases
Metallic character increases