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4th period d-block elements
4th Period
d-block elements center block of periodic table
transition elements d-sub level partially filled in one or
more oxidation state (ion charge) Except: Zn (full d-sublevel in all
oxidation states), Sc (common ion Sc3+ has no d electrons)
transition elements dense hard metallic relatively constant ionization energy similar chemical and physical properties 2+ oxidation state most stable (ex:
Cu2+)
transition elements…1. have a variety of stable oxidation
states.2. form complex ions.3. form colored ions.4. engage (take part in) in catalytic
activity.
1. Variation in oxidation states (ions)
3d and 4s sublevels are similar in energy
4s e- most often lost = 2+ oxidation state (very stable!)
d-block has higher ENC than s-block, but ionization energy does not increase very much going across the period because 3d and 4s have similar energy
Oxidation State Vanadium (V) reacts with zinc
amalgam (combination of two metals). Zinc is a reducing agent (donates
electrons) to change the oxidation state of the vanadium.
5+ 4+ 3+ 2+
Play the movie!
higher oxidation states are to the left of the d-block energy required to produce ions
increases going to the right a half-filled shell is more stable
than 3 or 5 valence electrons
21 22 23 24 25 26 27 28 29 30
Sc Ti V Cr Mn Fe Co Ni Cu Zn
4s23d1 4s23d2 4s23d3 4s13d5 4s23d5 4s23d6 4s23d7 4s23d8 4s13d10 4s23d10
+2, +3, +4
+2, +3,
+4, +5
+2, +3, +6
+2, +3,
+4, +7+2, +3 +2, +3 +2 +1, +2
ionization energy increases
higher oxidation states to left
2. Complex ions d-block ions have low-energy unfill
ed d and p orbitals can accept a pair of non-bonding elect
rons (ligand) form a bond between ligand and metal
ion ligand + metal ion = complex ion ex: water, ammonia (NH3), Cl-
all donate electron pair
M
Cl
Cl
ClCl
Complex ions
tetrahedral= 4 octahedral = 6 ligands ligands4 sides 8 sides
tetrahedron (tetrahedral)
Octahedron (octahedral)
number of ligands = coordination number
can bond once (monodentate) or twice (bidentate) complex ions:
stabilize transition metal affect solubility affect color
bite
Isomerism – compounds with the same formula, but different structures and bonding found in complex ions
stereoisomerism: isomers with different arrangements of atoms (bonding is the same)
cis (next to each other)
trans (opposite)
3. Colored Ions In most atoms, all d orbitals
have the same energy. In complex ions, d orbitals are
on TWO different energy levels. If surrounded by ions or some
kinds of molecules, an electric field effects the different orbitals differently.
White light passes through a transition metal and some frequencies are absorbed, some reflected
Some d electrons are moved to the higher energy d orbital.
Cu2+: red and yellow absorbed blue and green reflected
Color depends on ions surrounding transition element.
If no d electrons (Sc3+, Ti4+) colorless (no color)
white
light
lower d orbital
higher d orbital
4. Catalytic Activity catalyst: speeds up or begins a
reaction by using a different reaction “pathway”
because: complex ions can donate an e- pair they have many stable oxidation states
so they can easily gain and lose electrons in reactions
Fe2+ can easily become Fe3+ and still be stable!
d-Block Catalysts heterogeneous (common): the
surface of the transition metal or compound is an “active” surface for the reaction to occur on requires less activation energy activation energy: the level of
energy needed for a reaction to happen.
Heterogeneous Catalyst 2H2O2(aq) 2H2O(l) + O2(g)
reactants bond to the solid metal (Mn) surface which brings the molecules together.
N2(g) + 3H2(g) 2NH3(g) Haber Process Catalyst not used up in reaction
MnO2
Fe
homogeneous: the catalyst is in the same phase (state) as the reactants metal ion oxidized (e- lost) in one
stage, then reduced (e- gained) in the second
HomogeneousH2O2(aq) + I-(aq) I2(s) + H2O(l)
veeeeery slooooow reaction, very high activation energy
H2O2(aq) + 2H+(aq) + 2Fe2+(aq) 2H2O(l) + 2Fe3+
2I-(aq) + 2Fe3+(aq) I2(s) + 2Fe2+(aq)
two reactions are much faster, have lower activation energy
oxidized
reduced