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