Presentation on theme: "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."— Presentation transcript:
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 Sc 3+ has no d electrons)
transition elements dense hard metallic relatively constant ionization energy similar chemical and physical properties 2 + oxidation state most stable (ex: Cu 2+ )
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
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
21222324252627282930 ScTiVCrMnFeCoNiCuZn 4s 2 3d 1 4s 2 3d 2 4s 2 3d 3 4s 1 3d 5 4s 2 3d 5 4s 2 3d 6 4s 2 3d 7 4s 2 3d 8 4s 1 3d 10 4s 2 3d 10 +2, +3, +4 +2, +3, +4, +5 +2, +3, +6 +2, +3, +4, +7 +2, +3 +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 (NH 3 ), Cl - all donate electron pair
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.
Cu 2+ : red and yellow absorbed blue and green reflected Color depends on ions surrounding transition element. If no d electrons (Sc 3+, Ti 4+ ) colorless (no color)
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 Fe 2+ can easily become Fe 3+ 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 2H 2 O 2 (aq) 2H 2 O(l) + O 2 (g) reactants bond to the solid metal (Mn) surface which brings the molecules together. N 2 (g) + 3H 2 (g) 2NH 3 (g) Haber Process Catalyst not used up in reaction MnO 2 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
Homogeneous H 2 O 2 (aq) + I - (aq) I 2 (s) + H 2 O(l) veeeeery slooooow reaction, very high activation energy H 2 O 2 (aq) + 2H + (aq) + 2Fe 2+ (aq) 2H 2 O(l) + 2Fe 3+ 2I - (aq) + 2Fe 3+ (aq) I 2 (s) + 2Fe 2+ (aq) two reactions are much faster, have lower activation energy oxidized reduced