Transcript Periodic Trends/Patterns

Periodic Trends/Patterns
CH. 2
Periodic Trend
• Nuclear charge
• Reactivity
• atomic size or radius
• bonding characteristics
• ionization energy
• crystal configurations
• electron affinity
• acidic properties
• electronegativity
• densities
• metallic character
Quantum Mechanical Model
Effective Nuclear Charge: The s, p, d, and f orbitals
within a given shell have slightly different
energies.
The difference in energies between subshells result
in electron–electron repulsion which shields outer
electrons from the nucleus.
The net nuclear charge felt by an electron is called
the effective nuclear charge ( Zeff ).
Zeff
Quantum Mechanical Model
Zeff is lower than actual
nuclear charge.
Zeff increases
toward nucleus
ns > np > nd > nf
This explains certain periodic
changes observed.
*
Z
The effective nuclear charge in the actual
charge from the nucleus that an electron
feels due to attractive forces from the
nucleus but also repulsive forces from the
other electrons, mainly the core electrons.
Atomic radii
The Periodic Table 02
Periodic Properties 02
Atomic Radii 02:
Ions and Ionic Radii02
Chapter 06
9
Ions and Ionic Radii
Trend of ionic radii
The cation of an atom decreases in size while
the anion of an atom increases in size.
The trend can not be made according to the
periodic table, but by the isoelectronic series.
The more positive an ion is the smaller it is
because Zeff increases, while the more
negative an ion, the larger it is because Zeff
decreases.
Ionization Energy
Defined as the amount of energy necessary to
remove the outermost electron from an
isolated neutral atom in the gaseous state to
infinity.
Abbreviation is Ei, it has units of kJ/mol.
IE
successive ionization energy
Ionization Energy
Minor irregularities in the Ei values are explained
by looking at the electron configurations.
IE Trend
Ionization Energy
Ionization energies vary periodically, which is
explained by the changes in Zeff .
Zeff
Electron Affinity
01
Electron Energy: Energy change that occurs when
an electron is added to an isolated atom in the
gaseous state.
Abbreviation is Eea, it has units of kJ/mol. Values are
generally negative because energy is released.
Value of Eea results from interplay of nucleus
electron attraction, and electron–electron
repulsion.
EA
Electron Affinity
02
EA Trend
Periodic properties REACTIVITY Li
Periodic properties - Na
Periodic properties - K
Metallic Character
• The metallic character of atoms can be
related to the desire to loose electrons
• On the periodic table, the metallic character
of the atoms increase down a family and
decreases from left to right across a period.
Periodic Trend Activities
• WebElements
• Periodicity and Properties of Elements and
Compounds: An Internet Study
• Periodic Trends Lesson
• Periodic Table Exercises
• Our Favorite Element
• Structured Curriculum Lesson Plans