Download Elements, basic principles, periodic table

8/24/16
BASICS
OUTLINE
•  Periodic table & electronic configurations.
•  Periodic properties: ionic radius, electron negativity,
1st ionization potential
•  Covalent & ionic bonding
•  Hybridization and molecular orbitals
•  Reactions (part 1)
WHITE (CH 1)
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WHY DOES IT LOOK LIKE THIS?
Chemical behavior controlled by electrons Elements in same columns (periodic behavior) behave similarly due to similar electron configura:ons. Outer most electrons most important in chemistry since more readily lost and/or shared (= interac:on) In contrast, inner electrons are :ghtly bound to the nucleus by electrosta:c forces. 2
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Electrons and orbitals •  Orbital describes where electron could be. •  2 electrons “fill” an orbital “s”
3 “p”s
–  “s” orbitals spherical –  “p” pairs of “lobes” –  “d” &”f” more complex •  Orbital geometry control how electrons are shared => molecular geometry 5 “d” s
Note: the 14 “f”s are not shown
Filling of 1s orbital – how many columns?
Filling of higher “s” orbitals
“d” orbitals!
How many columns?
“p” orbitals! Count
columns?
“f” orbitals! Count columns
Filled orbital assignment shorthand notation:
Ne = 1s2 2s2 2p6 and Ar = [Ne] 3s2 3p6.
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Electron configuration – packing all those electrons
Aufbau Principle Simplified
!  Low energy orbital fills 1st.
!  s: 2, p: 6, d: 10, f:14, (in sets of 2:
1*2, 3*2, 5*2, 7*2)
!  Each set of 2 can host 2 e- with
opposite spin
Electron configurations w/ full or half-full orbitals are
“preferred” because they are more stable.
!  full = orbitals with paired spins
!  half = only 1 spin direction (e.g. p with 3*1e- )
Review Periodic Properties from Introductory Chemistry
1. Atomic radius:
►Radii of the elements
increase down a column
decrease across a row (left to right).
2. Ion size (ionic radius)
+ ion smaller than the neutral atom
b/c fewer e- feel the "pull" of the positively charged nucleus
- ion is larger than the neutral atom
Ions behave the same as atoms across the periodic table (row vs column
Importance of the radius: molecules can only “fit” certain sizes
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ionic radii of common ions in common ionization state
Remember: many elements have more than one stable “valance”.
Elements lettered in red have active “redox” chemistry in nature = important
for environmental behavior.
Remember: oxidation = loss of electrons; reduction = gaining electrons.
Ionization and Ionization Energy (aka ionization potential):
Ionization energy measures how easy or hard it is to remove an
electron from an element or ion.
Energies of filled electronic orbitals give rise to common
oxidation states for individual elements.
Electronic structure determines ionic charge and IE.
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Oxidation states and the periodic table
►noble gasses have filled
valence shells. They rarely
ionize (except Xe), or interact
►all other elements “want to” fill
their valence shells too.
Examples
► the element Cl = [Ne]2s2 3s2 3p5 acquires 1 electron to become Cl- = [Ar] configuration.
► the element K = [[[Ar]4s1 loses 1 electron to attain an [Ar] electronic configuration (K+ = [Ar]).
Low IP
But use caution with a generalization
like this, because other
factors come to bear
High IP
Noble gas: filled shell
high IP: hard to remove e-
Would rather
gain e- instead of
losing 1: high IP
Low IP to lose
e- for a filled shell
IP = ionization potential
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Electronegativity
Measures desire to gain an electron. Classification by
electronegativity as:
a. donors (+ ions)
Low electronegativity = nearly
empty valence shell= gives up
electrons easily
b. acceptors (- ions)
high electronegativity = mostly
filled valence shell
c. inert (noble gases).
Electronegativity ≥ 2.5 is a
quasi chemical dividing line
GG325 L2, F2013
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Bond Character
All about e- sharing, but not all bonds share e- equally.
Two end members:
- Pure Covalent Bond = 2 atoms bond with same electronegativity
spectrum of options in between
- Pure Ionic Bond = largest possible electronegativity difference
Bond character affects how ionically-bonded solids ("salts") and
covalently-bonded solids (quartz, octane, etc..) behave in H2O
and air.
Bond orbitals
Atomic orbitals combine and "hybridize" to make bonding and
non-bonding orbitals that define electron density between atoms.
e.g. sharing between
2 s orbitals
s and p orbital,
2 p orbitals
But some elements have more to share…
http://chemwiki.ucdavis.edu/Organic_Chemistry/Organic_Chemistry_With_a_Biological_Emphasis/…
…Chapter__1%3A_Chapter_1%3A_Introduction_to_organic_structure_and_bonding_I/…
…Section_1.5%3A_Valence_bond_theory%3A_sp,_sp2,_and_sp3_hybrid_orbitals
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Combo example: sp3 hybridization
Simplest: element with s + p valence:
Tetrahedral
coordination
hybridize
Remind you of anything?
http://chemwiki.ucdavis.edu/Organic_Chemistry/
Organic_Chemistry_With_a_Biological_Emphasis/
Chapter__1%3A_Chapter_1%3A_Introduction_to_organic_structure_and_bonding_I/
Section_1.5%3A_Valence_bond_theory%3A_sp,_sp2,_and_sp3_hybrid_orbitals
If there’s too many or too few electrons for this:
Nitrogen
Oxygen
sp2 hybridization (planar geometry)
Ex. Carbon double bond:
Together make planar set of bonds + perpendicular 2pz
planar
Planar geometry makes 1 carbon bond, unhybridized p orbital makes π
bond, the second (double). This locks molecule: no rotation of left vs right
http://chemwiki.ucdavis.edu/Organic_Chemistry/
Organic_Chemistry_With_a_Biological_Emphasis/
Chapter__1%3A_Chapter_1%3A_Introduction_to_organic_structure_and_bonding_I/
Section_1.5%3A_Valence_bond_theory%3A_sp,_sp2,_and_sp3_hybrid_orbitals
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sp2 hybridization in the carbonate anion = CO32Electron DELOCALIZATION
O
Ver:cal orbitals make π system C
O
O
http://pages.swcp.com/~jmw-mcw/Parsing%20spdf%20orbital
%20hybridization.html
Other bonding interactions – hydrogen bonding
-Average electron density around O in H2O is 10x greater than around H
-Exposes the “naked” protons of H -> molecule partial positive charge
-Leads to hydrogen bonding
δδ+
δ-
δ+
δ+
δ+
http://chemwiki.ucdavis.edu/Organic_Chemistry/
Organic_Chemistry_With_a_Biological_Emphasis/
Chapter__1%3A_Chapter_1%3A_Introduction_to_organic_structure_and_bonding_I/
Section_1.5%3A_Valence_bond_theory%3A_sp,_sp2,_and_sp3_hybrid_orbitals
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Hydrogen bonding
Chemical reactions
6 geochemically pertinent chemical reaction types below:
Reminder: liquid, vapor, solid and aquous (dissolved)
1. Phase change
H2O(s) ↔ H2O(l) ↔H2O(g)
drives the hydrologic cycle.
CaCO3 (s) (aragonite) ↔CaCO3 (s) (calcite)
formation/preservation of carbonate sediments
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Chemical reactions
2. Bond Reorganization
The Redfield equation of Photosynthesis/Respiration :
106CO2 +16NO3- + HPO42- + 122H2O +18H+
↑↓ƒ„
C106H263O110N16P + 138O2
or (CH2O)106(NH3)16(H3PO4) + 138O2
the "Urey" rxn: understanding rock weathering and global
controls on atmospheric CO2:
CaSiO3(s) + CO2(g) ↔ CaCO3(s) + SiO2(s)
Chemical reactions
3. Dissolution/precipitation & Dissolution/gas release
CaSO4(s) ↔ Ca2+(aq) + SO42-(aq)
NaCl(s) ↔ Na+(aq) + Cl-(aq)
CO2 (g) ↔ CO2 (aq)
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Chemical reactions
4. Oxidation/Reduction - "Redox": electron transfer
MnO2(s) + 4H+ + 2Fe2+(aq) ↔ Mn2+(aq) + 2H2O + 2Fe3+(aq)
An important reaction all over the hydrosphere/geosphere
Photosynthesis/Respiration is in this category too
5. ion substitution
We’ll see a number this semester.
Na+ (aq) + [clay mineral]-K+ ↔ K+ (aq) + [clay mineral]-Na+
cation exchange between a clay mineral and ions in water
Chemical reactions
6. Complexation/Chelation
Fe2+(aq) + 6H2O ↔ Fe(H2O)62+ (aq)
hydration of Fe2+ in water
aqueous metal complex with dissolved organic carbon
EDTA
A common multidentate ligand
(EDTA: ethylenediaminetetraacetic acid)
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Complexation/chelation
Complexes involve ligands and host ions.
Ligand: ion/molecule that binds to a central metal atom; host:
metal atom
Hydration is type of complexation reaction; ligands are water:
Fe2+ + 6H2O ↔ Fe(H2O)62+
H2O stabilizing Fe2+ ion with electron pair.
The hydrate itself involves 5 other water molecules.
More on ligands
Unidentate: offer electrons from a single site to a complex; ex: H2O,
Cl- (chloride) and :NH3 (ammonia).
All of the following complexes are possible:
[FeCl6]-3 [FeCl3(NH3)3]0 [FeCl2(NH3)4]+ [Fe(NH3)6]+3
Relative proportions will vary with pH since NH3 + H+ ↔ NH4+
(ammonium is not a good ligand)
At low pH [FeCl6]-3 would be favored
GG325 L3, F2012
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More more on ligands
Chelation complexation that involves multidentate ligands.
A chelate is complex with multidentate ligand.
A multidentate ligand more than 1 e- pair to donate to cation.
Simplest is:
bidentate ligand has 2 active binding sites for a cation.
e.g., ethylene diamine,
:NH2-CH2-CH2-H2N:
and oxalic acid/oxylate anion
More more more on ligands
Bidendate ligands can bind in two ways:
cis: next to
trans: across
M is a metal or other cation and B is where the donor electron pairs are in
the ligand.
"small" bidentate ligand such as ethylene diamine (NH2-CH2=CH2-NH2) usually
bind cis for geometric reasons.
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