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Periodic Trends (Chapter 9 (Atomic Parameters (Atomic Radii
Increase…
Periodic Trends
Chapter 9
Atomic Parameters
Ionization Potential
- The energy required to remove an e- [Positive Numbers]
- Decreases down column (based on Zeff)
- Increases across row (based on Zeff)
- Filled and Half-Filled shells have high Ionization Energies
- D block elements (and f too), lose the [S] Orbital e- first in solutions
- If you had Co [Ar] 3d7 4s2 -> Co2+ [Ar] 3d7
Electron Affinity
- the energy released upon gaining an e- [Negative Numbers]
- Greater nuclear charge means higher electron affinity
- If easy to add an e- = high e- affinity
- if energy is released [+] = Favorable
- If energy is required [-] = UnFavorable
Atomic Radii
- Increase Down Column
- Decrease Accross period
Penetration
- how effectively electrons can get close to the nucleus
Shielding
- The reduction of the true nuclear charge to the effective nuclear charge by the electrons
Lanthanide Contraction
- f and d electrons are poor shielders
- Ex: Mo and W are the same size
ElectroNegativity
- Avg of Ionization Energy and Electron Affinity
- Increase Across a Row
- Decrease Down Column
- Exception: Alternation Effect
Diagonal Relationships
- Lower Right Position has similar:
- Atomic Radii
- Charge Densitiy
- Electronegativity
- Many Chemical Properties
Enthalpies of Atomization / Melting Point
- Measure of the energy required to form gaseous atoms
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- S and P Orbitals
- Increases Until C or Si; Then Decrease
- Decreases Down a group
- Become less effective at forming bonds as the period number increases
- Become too difuse for extensive overlap
- D Block
- Increases Down a group
- Become more effective at forming bonds as the period number increases
- Become Optimal For Overlap
Occurance
- "In Nature"
- Soft w/ Soft
- Hard w Hard
Siderophiles
- Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Rh3+, Ir3+
Chalcophiles
- Pd2+, Pt2+, Pt4+, Cu+, Ag+, Au+, Hg2+, Tl+, Pb+
Lithophiles
- H+, alkali+, alkaline earth2+, Sc3+, Ln3+(4f), An3+(5f), Ti4+, Cr3+, Fe3+, Co3+, (Mn2+ = Breaking Point)
Atmophiles
- Gases such as H, N, and Noble Gases
Valence Electron Configurations
Metallic Character
- The ability to lose an electron to form the electron sea
- Binds together cations and accounts for metallic bonding
- Decreases Across a Period & Increases Down a Column
- Many Elements in p-block exist as allotropes (2 or more physical forms)
- Low IE = Metals
- High IE = NonMetals
- Down a Column, elements become more metallic
- Across a row the elements become less metallic
Coordination Number
- Increases Down Columns
- Increases as Radius Increases
- Possibly due to being able to fit more ligands around the central atom
Oxidation States
- Inert Pair Effect
- Heavier p block elements form compounds with the element with an oxidation number of 2 less than the group number (# - 2)
- Oxidation Number (# - 2) stability increases down the group
- Group Oxidation Number is achieved in d block only for Groups 3-8
- Highly oxidizing F or O are required to do this
- Beyond the D5 electron confg. high oxidation states are not observed
- The tendency for the d electrons to participate in bonding decreases
- However, stability of high oxidation states increases down a group (Groups 4-10) as the atomic radius increases.
Bond Enthalpy
- The Average bond dissociation enthalpy taken over a series of compounds
- P block, E-H bonds get weaker down a column
- Bond Enthalpy Decreases down a column
- D block, E-H bonds get stronger down a column
- Bond Enthalpy Increases down a column
- Lone pair atoms typically decrease in bond enthalpy down a column
Chapter 1
Ionization Potential
- The energy required to lose an e- [Positive Numbers]
- Decreases down column (based on Zeff)
- Increases across row (based on Zeff)
- D block elements (and f too), lose the [S] Orbital e- first in solutions
- If you had Co [Ar] 3d7 4s2 -> Co2+ [Ar] 3d7
Electron Affinity
- the energy released upon gaining an e- [Negative Numbers]
- If easy to add an e- = high e- affinity
- Energy Released [+] = Favorable
- Energy required [-] = UnFavorable
Atomic Size
- Decrease Across Row & Increases Down Column
- Due to Higher Nuclear Charge [+]
- Lanthanide Contraction
- La3+ 130 pm (8-coord)
- Yb3+ 112 pm (8-coord)
- You see a decrease in size due to increase in effective nuclear charge (Zeff)
- 3d orbital contraction
- Ti2+ 1.0 A (6-coord) vs Zn2+ 0.88A (6-coord)
Shielding
- Amount of + charge from the nucleus experienced by e-
- Related to Zeff
- 1s orbitals have higher Zeff and thus lower shielding
- D orbitals have lower Zeff and thus higher shielding
- V e- are more shielded than core e-
- As oxidation state increases, size decreases (shielding)
- Removing an electron
- Ru 3+ = 0.82A vs Ru8+ =0.50A
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