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Concepts for Midterm II

Textbook Reading/Sections

General Concepts

  • Trends in metal and atomic radii
  • Electronic structure of Transition metals and corresponding ions
  • How magnetism occurs. What is para- and dia-magnetism
  • Definition of complexes, including both inner vs. outer sphere groups.
  • Identify atoms on a polyatomic ligand that will bind to a metal
  • How to form a Coordinate covalent bond.
  • How polydentate ligands do their stuff. Some thermodynamics of the chelate effect.
  • Identify the five types of isomers discussed in class
  • How does optical Rotation play a role in optical isomers
  • How spectroscopy can be used to tell information about crystal field splitting of complexes.
  • If given two structure, determine if they are isomers of each other
  • Which d orbitals will be stabilized and destabilize by a ligand field and why!
  • How to use the spectrochemical series for crystal field slitting understanding
  • How to determine when a complex will be high spin or low spin based on ligands, crystal field splitting parameters and electron pairing energies.
  • Using and calculating Kf for complexes
  • Connect thermodynamics to polydentate ligation.
  • Main properties of each group in the periodic table: including preferred oxidation state, and simple reaction (H20, O2, Cl2 etc.)
  • What distinguishes a metal from a non-metal
  • Ionization energy vs. reduction potential for alkali metals
  • Name several allotropes for key elements (e.g. O, C, P, S, Sn, etc)
  • How to make noble gases react.

Terms

  •  Poor metals
  •  Self-passivation
  •  Amphoteric
  •  Allotrope
  •  Noble gas
  •  Interhalogens
  • Buckyballs/Nanotubes
  • Glass
  • Solvated Electron
  • Metals
  • Alkaline Earth metals
  • Alkali Metals
  • Amalgam
  • diamagnetism, paramagnetism
  • Lanthanide contraction
  • Steel
  • Ores
  • High Spin/Low Spin
  • Aufbau Principle
  • Hund’s Rule
  • cis, tran isomers
  • mer, fac isomers
  • ROYGBIV
  • Color wheel
  • Complementary colors
  • Spectroscopy
  • Crystal field splitting
  • High field splitting ligand
  • Coordination number
  • Octahedral, tetrahedral, square planer, linear, bend geometries
  • Chiral
  • enantiomers
  • Atomic orbital
  • Lanthanide contraction
  • Shielding
  • Spin
  • Coordination number
  • Coordination sphere
  • Donor atom
  • Ligand
  • Chelate (and chelation)
  • Degenerate
  • Chirality
  • Optical active
  • Spectrochemical series
  • Pairing energy
  • Hydride
  • Nitride
  • Oxide, superoxide, peroxide
  • Inert pair effect
  • Monodentate, bidentate, polydentate
  • Stereoisomers and structural isomers
  • Metal, non-metal, and metalloid or semi metal
  • Ferromagnetism, paramagnetism, diamagnetism
  • Strong field ligand and weak field ligand 

General Concepts

  • Trends in metal and atomic radii
  • Transition Metals
    •  DECREASE left to right BUT INCREASE at the end of each series (starting around 8B)
      • Why? – When you begin to pair up the electrons in the d orbitals, the electrons begin to repel and increase the atomic radius
      • Note: when the radius gets smaller, the density gets larger and the melting point increases (smilie face, frown, frown)
      • Lanthanide Contraction: The 3rdand 4th transition metal periods have almost the same radius as the period 5 elements (2nd row of transition metals) as the f-block electrons do a poor job shielding    

Electronic structure of Transition metals and corresponding ions

  • ns2ndx with x=1-10
  • Note: these metals lose electrons from their s orbitals first (e.f,
  • Sc: 3d14s2
  • Mn: 3d54s2
  • Exceptions (partially and full filled sub-shells):
  • Cr: 3d44s2  -is really  3d54s1
  • Cu: 3d94s2 -is really 3d104s1

How magnetism occurs

  • What is para- and dia-magnetism
    • Paramagnetic = unpaired electrons, pulled into a magnetic field
    • Diamagnetic = no unpaired electrons, not attracted to or repelled from a magnetic field
    • To figure this out, find the electron configuration of the atom and draw the crystal field splitting (for d4-d7)
    • Note: Spin (aka magnetic moment) = # of unpaired electrons/2

Definition of complexes, including both inner vs. outer sphere groups

  • Complex – any chemical species involving coordination of ligands to a metal center
  • Ex. [Co(NH3)3]3+ = Complex Cation
  • Ex. [CoCl3(NH3)3] = Neutral Complex
  • [Inner Sphere]Outer Sphere = [Metal/Ligands]Counterions (to balance charge)
  • Identify atoms on a polyatomic ligand that will bind to a metal

•      See spectrochemical series Link: Ligands

How to form a Coordinate covalent bond

  • Ligands act as Lewis Bases and donate their electron pairs (both elections) to the metal atoms/ions to form coordinate covalent bonds
    • Monodentate – donates 1 electron pair (e.g.. CN- and Cl-)
    • Bidentate – donates 2 electron pairs (e.g., en and ox2-)
  • Polydentate – donate 2+ electron pairs (eg., hexadentate (6 “bites”))

How polydentate ligands do their stuff. Basic thermodynamics of the chelate effect

  • Chelation – process of a polydentate ligand attaching (“biting”) to a metal to produce a ring [Chelate = claw]
  • Entropically favored and possibly enthalpically driven

Ex. [Co(H2O)6] + en ->  [Coen(H2O)4)] + 2H2O

2 species                      3 species

  • Entropy increases

Identify the five types of isomers discussed in class

  • Structural: different connectivity of atoms
    • Ionization – interchange the ions inside and outside of the coordination sphere
      • Ex. [CrSO4(NH3)5]Cl and [CrCl(NH3)5]SO4
    • Coordination – there is a swap in ligands between the anionic and cationic coordination spheres in a multi-coordination complex
      • Ex. [MX][M’Y] and [MY][M’X]
    • Linkage – differs in which atom is bound to the metal complex
  • Ex. M-ONO and M-NO2
  • Sterioisomers: different arrangement of atoms in space
    • Geometric (cis/trans)
      • Cis – 90° apart
      • Trans – 180° apart
    • Geometric (cis/trans)
      • Mer – on the same meridian (cis-trans-cis)
      • Fac – on the same face (cis-cis-cis)

How does optical Rotation play a role in optical isomers

  • It has NO optical isomers if:
  • There is ANY plane of symmetry (they can be in weird places)
  • It is invertible (you can invert the top and the bottom through the center and get the same molecule out)
  • It is optically active and has optical isomers (entantionmers) if:
  • The mirror image of the molecule is NONsuperimposable on the original object
  • It is chiral

How spectroscopy can be used to tell information about crystal field splitting of complexes.

  • A wavelength corresponding to a color in the visible light spectrum is produced when a photon of light is absorbed and an electron in the d orbital is excited to a different energy state
  •  Note: d0 and d10 compounds are colorless (either there is no electron to excite or there is no place for the electron to go)
  • Strong Field ligands have a large delta o and they absorb high energy light which corresponds to shorter wavelength. Shorter wavelengths of light are around violet and reflect their opposite (complementary) color. For a compound absorbing violet, the compound reflects and looks yellow
  • Weak field ligands have a small delta o and they absorb low energy light which corresponds to longer wavelength such as red light. The complementary color is reflected and is what we see. For a compound absorbing red light we would see green (like plants!)
  • How \(\Delta_o\) and color are related: \(\Delta_o = \dfrac{hc}{\lambda}\)
    • Note: a compound only absorbs light when radiation from the photon has the right energy to move an electron from a low energy level to a higher one (in other words, when the above equation is true)
    • (Crystal Field Theory concerns electrostatic attractions)

If given two structure, determine if they are isomers of each other

  • Check via optical isomer rules
  • Look for a plane of symmetry of a point of inflection (if you find one, it is not optically active)
  • Take the mirror image, rotate it, and see if you can superimpose it (if you can, it is not optically active) – you can’t fold the paper over!
  • Other “Guidelines”

Octahedral

Geometric Isomers

ML6

None

ML5X

None

ML4X2

(2) Cis and trans

ML3X3

(2) Fac and mer

MA2B2C2

(5) trans-trans-trans; trans(A)-cis-cis; trans(B)-cis-cis; trans(C)-cis-cis; cis-cis-cis (this one has an optical isomer)

 

Tetrahedral

No Geometric Isomers – all atoms are equidistant from the center metal atom

ML4

 

ML3

 

ML2X2

 

MA2X2

 

MA2XY

 

MABCD

This one can have an optical isomer because all of the ligands are different

 

Square Planar

Geometric Isomers

ML4

None

ML3X

None

ML2X2

Cis and trans

ML2XY

Cis and trans

 

Which d orbitals will be stabilized and destabilize by a ligand field and why!

How to use the spectrochemical series for crystal field slitting understanding

How to determine when a complex will be high spin or low spin based on ligands, crystal field splitting parameters and electron pairing energies.

•      See your discussion on Crystal Field Theory

Using and calculating Kf for complexes

  • Idea: ligands can “come off” and be exchanged for other ligands (preferably polydentates for monodentates due to the entropic effect)

Kf = K1*K2*K3

Kf = [Products]coefficient/[Reactants]coefficients

  • Note: This “reaction” does not occur all in one step; it occurs in multiple steps that end up canceling out to get the final Kf
  • Connect thermodynamics to polydentate ligation.
    • Chelation – process of a polydentate ligand attaching (“biting”) to a metal to produce a ring [Chelate = claw]
    • Entropically favored (e.g.)

[Co(H2O)6] + en --> [Coen(H2O)4)] + 2H2O

2 species                      3 species

  • Entropy increases

Main properties of each group in the periodic table: including preferred oxidation state, and simple reaction (H2O, O2, Cl2 etc.)

What distinguishes a metal from a non-metal

  • Metal:
    • Good conductors of heat and electricity
    • Malleable
    • Ductile
    • Moderate to high melting points (except poor metals)
    • LOSE electrons
  • Nonmetal:
    • Poor conductors
    • Brittle
    • GAIN electrons  

Ionization energy vs. reduction potential for alkali metals

  • Ionization Energy is for a metal in gaseous phase
  • Reduction potential is for a metal in its aqueous phase – hence the difference between the two “reactivities”

Name several allotropes for key elements (e.g. O, C, P, S, Sn, etc)

  • Oxygen: O, O2 , O3
  • Carbon:
    • Graphite
    • Fullerenes
    • Diamond
  • Phospohorus
    • Red Phosphorous (3 joined together)
    • White Phosphorous (the dangerous, less stable one)
  • Sulfur: S2, S4, S6, etc.
  • Tin
    • Grey Tin
    • White Tin (the one that falls apart that supposedly caused the buttons of Napoleon’s army to disintegrate in the cold Russian winter). Perhaps happened..but likely not

How to make noble gases react

  • Get a really electronegative nonmetal and high temperatures

 Xe + F2 ---> XeF2