transition metals Flashcards
atomic radii in d block periodic trend
The opposite of electronegativity because more protons pull electron cloud closer
transition metal definition
An element that forms one or more stable ions with incompletely filled d-orbitals
electron filling order
aufbau order: 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10
electron removal order
1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6
what causes colorful compounds
electronic transfers between d orbitals, if d orbitals are empty or completely full then cannot occur
diamagnetic
no unpaired e-, no response to a magnetic field
paramagnetic
some unpaired e-, responds to a magnetic field. greater number of unpaired e-, greater response
ligands
- chemical species with several neutral or anion molecules boding to transition metal ion (or atom)
- anything with long pair can act as a ligand
are ligands lewis acids or bases
ligands are lewis bases (e- pair donor)
are metal centers lewis acids or bases
metal centers are lewis acids (e- pair acceptor)
draw hexaaquanickel(II), CN, molecular geometry
practice drawing polydentate ligands
polydentate ligands application
polydentate (bi,tri,tetra,penta,hexa,etc) are good chelating agents— help bind up or isolate metal by making two or more connections to it
polydentate ligand application example
EDTA for lead poisoning
CN, geometry, and name for [Co(OH2)6]2+ and [CoCl4]2- draw using wedge and dash
check tn pg 20
square planar complex example [Pt(NH3)2Cl2] draw all isomers
check tn pg 21
stereoisomers
Same atoms, same connectivity (what’s bonded to what)
- Geometric isomers: different arrangement of atoms (ex: cis and trans, fac and mer)
- Optical/chiral isomers (enantiomers:) same arrangement of atoms but not the same molecule
write formula and draw: sodium chloro(oxalato)-fac-trpyridinestannate(II)
check tn pg 24
opitical/chiral isomers characteristics
- must be 3D molecule such as tetrahedral or octahedral (square planar is not 3D)
- two objects are chiral if they are non-superimposable mirror images (no mirror planes)
- in organic molecules, tetrahedral carbon atom will be a “chiral center” if it has 4 different atoms or groups bonded to it
draw all stereoisomers for [Co(H2)2(ox)BrCl]-
check tn pg 29
structural isomers
complexes with same atoms but different connectivity: 3 types
linkage isomers
same ligand, bonded through different atoms
ionization isomers
a ligand and counter ion switch places
coordination isomers
different metal in center, same CN environment (ligands and geometry are the same)
ligands that don’t do linkage isomerism
CN-, CO
practicing drawing isomers notes
tn pg 36-37
highly colored ions have
partially full d-orbitals
colorless ions have
empty or full d-orbitals
crystal field theory
- ionic model of metal-ligand bonding
- metal cations viewed as “point” of positive change
- metal cation electrons in d orbitals are regions of negative charge
- ligands are viewed as “point” negative charges
Ligands surrounding a metal present in a field of negative charge concentrated in specific regions depending on geometry
sketch dyz
clover shape on x axis and between y and z
sketch dxz
parallel to z axis/off all axes
sketch dxy
off x and y/z, on with z/ filling gap
sketch dx2-y2
on y and x axes
dz2
doughnut
features of orbitals: lobes
regions of orbital with highest probability of e- present
node
region where probability of finding e- is zero. where wave function changes sign and diagram color changes red to blue
on/off axes
lobes and nodes can be on the x-y-z axes (on axes) or in between (off axes)
interaction between d-orbitals and ligands
In CFT model, negatively charged e- on TN mental (core and valence) repel negatively charged e- of ligands
CFT overlap and energy
more overlap=more repulsion-higher energy
ground state e- configuration
determining pairing energy (P.E.: energy required to pair e- in an orbital) and splitting energy (delta o: difference in energy between d orbitals)
strong field
large delta o, low spin, fill lower before moving to higher row because it takes too much energy
weak field
small delta o, high spin, fill all rows at same time because takes less energy and is “closer”
practice tn pages 50-57
do it bitch
octahedral vs. tetrahedral splitting energy
octahedral is most common geometry for complexes, tetrahedral geometries do not have d-orbitals directly pointing towards ligand, so no strong field effect
spin of tetrahedral complexes
all tetrahedral complexes are high spin
geometries have different CFT energy level diagrams: sketch and check
complex absorbs light at wavelength, what is ligand field splitting energy for complex in kj/mol
check
use crystal field theory to predict geometry for CN=4 [Ni(CN)4]2-
[Ar] 3d8 diamagnetic
Molecular orbital theory
- explains the spectrochemical series and bonding in transition metal complexes better than CFT
- leading theory for transition metal complexes is Ligand Field Theory–generic degenerate “ligand group” orbitals, one for each ligand.
- sigma bonding interactions set up overall orbital energy level diagram and degree of pi back-bonding determines energy of delta o
what establishes the spectrochemical series of ligands
difference in pi bonding
scandium family
- common O.S. = 0, +3
- some similar chemistry to Mg
- No d-electrons in ions: colorless and diamagnetic
titanium family
- common O.S.= 0, +4
- some similar chemistry to C, Si
- structurally strong, very lightweight metal
- great for bicycle frames, airplanes
- TiO2 is very white, brighter paint and paper
Vanadium family
vanadium:
- common O.S.= 0, +5
- used in alloys to strengthen material
-toxic!
niobium (Nb) and Tantalum (Ta)
- named after greek mythology daughter and father
- Nb is a material of interest for superconductors
Chromium family
Cr:
-common O.S.= 0, +3, +4, +6
- first name derived from greek word for color, “chroma”
-toxic!
Mo and W:
-biologically important for enzymes, pigments
- W has very high melting point
- used for light bulb filaments, heat lamps
Manganese family
- Mn has most oxidation states of first row TN metals
- not found in nature as a pure metal– always in ore
- used as a catalyst in alkaline batteries, strengthening component in steel, and as a cofactor in many enzymes
Tc:
- lightest radioactive element ( a beta emitter)
- only man made, discovered in 1937
Iron family
Fe:
Common O.S.= 2+, 3+
Possible O.S.= 2+, 6+
- most important element for modern civilization- major component of steel
- most common element on earth by mass
- biological importance for oxygen transport in vertebrates, redox enzymes in plants and animals
Cobalt family
Co:
- beautiful blue color, rare to find pure, common in ores with smelly biproducts
Rh:
- hard, corrosion resistant, chemically inert
-rare, good for plating jewelry
Ir:
- rare, comes from space, used as tracer to develop and support theories about when asteroids hit earth
Nickel family
Ni, Pd, Pt:
- stable, less reactive metals, all good catalysts
Ni applications: coins, batteries, corrosion prevention
Pt: rare, un reactive, corrosion resistant, used for inert electrodes, jewelry, anti-cancer drugs
Copper family
Cu: excellent conductor of electricity, durable, alloys: Cu/Sn- bronze, Cu/Zn- brass
Ag: highest thermal conductivity, electrical conductivity, and reflectivity, more abundant than Au, tarnishes from contact with sulfur
Au: very un reactive, even to acids, most malleable metal, used for jewelry, currency
Zinc family
some similar chemistry to Mg
Zn: corrosion resistant, toxic
Cd: toxic, common O.S.= 2+ (used in batteries)
Hg: only metal liquid at room temp, toxic, dental fillings
