periodic table and periodicity. dmitri mendeleev “the elements, if arranged according to their...
TRANSCRIPT
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 familiesValence electrons
• C. Nonmetals- Halogens- Noble gases
• B. Metals - Alkali metals
- Alkaline earth metals - Transition metals - Inner transition metals
- Representative elements
• D. Semimetals/metalloids
Ionization Potential/EnergyIE: Energy required to remove e-
Higher the IE: more difficult to remove e-
Across PeriodIE INCREASES* as the number of protons increases
* with decrease @ each subshellWhy? (effective nuclear charge)
Down GroupIE DECREASES as the number of shells
increasesWhy? (shielding, effective nuclear charge)
Electronegativity
The ability to attract e-
Across PeriodEN INCREASESBecause nuclear charge (# p+) increases
Down GroupEN DECREASESBecause more shells (n), more shielding, e- further away from nucleus
Atomic Radius
Across PeriodAtomic size DECREASES!Because nuclear charge (# p+) increases, as e- are added to same shell (n), pulls e- in tighter
Down GroupAtomic size INCREASESBecause more n (shells), more shielding,
e- further away from nucleus
Ionic Radius
IonCharged atom
CationPositive (+) ion (neutral atom looses e-)
AnionNegative (-) ion (neutral atom gains e-)
IsoelectronicSame electron structure
Ionic Radius
Across Period
IR DECREASES* (why?)
* with jump up in size @ metalloids!
Down Group
IR INCREASES
Compare to neutral atom
Valence e- are the outermost e- of an atom
D. Metallic character/nonmetallic character
Metallic CharacterIncreases
Nonmetallic character increases
Metallic Properties
Across Period
Metallic Properties DECREASES
Down Group
Metallic Properties 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