Transcript 4th period d-block elements

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
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
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

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 sblock, 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, +2, +3, +2, +3, +2, +3,
+2, +3 +2, +3
+4
+4, +5
+6
+4, +7
+2
+1, +2
ionization energy increases
higher oxidation states to left
2. Complex ions
 d-block ions have low-energy
unfilled d and p orbitals
 can accept a pair of non-bonding
electrons (ligand)
 form a bond between ligand and
metal ion
 ligand + metal ion = complex ion
 ex: water, ammonia (NH3), Cl all donate electron pair
Complex ions
Cl
M
Cl
Cl
Cl
tetrahedral= 4 octahedral = 6
ligands
ligands
4 sides
8 sides
tetrahedron (tetrahedral)
Octahedron (octahedral)
 number of ligands =
bite
coordination number
 can bond once (monodentate)
 or twice (bidentate)
 complex ions:
 stabilize transition metal
 affect solubility
 affect color
 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)
higher d orbital
white
light
lower 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
MnO2
 2H2O2(aq)  2H2O(l) + O2(g)
 reactants bond to the solid metal
(Mn) surface which brings the
molecules together.
Fe
 N2(g) + 3H2(g)  2NH3(g)
 Haber Process
 Catalyst not used up in reaction
 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
Homogeneous
H2O2(aq) + I-(aq) I2(s) + H2O(l)
veeeeery slooooow reaction, very high activation energy
oxidized
H2O2(aq) + 2H+(aq) + 2Fe2+(aq)  2H2O(l) + 2Fe3+
2I-(aq) + 2Fe3+(aq) I2(s) + 2Fe2+(aq)
reduced
two reactions are much faster,
have lower activation energy