Chapter 3 Notes: First-row d-block Elements Chapter 13.1: The transition elements have characteristic properties; these properties are related to their all having incomplete d sub-levels Chapter 3 Notes: First-row d-block Elements

Important terms for this section Magnetic properties Diamagnetism Paramagnetism Ferromagnetism Domains General notes about first-row d-block elements Tends to have a “lull” in periodic patterns Have similar chemical and physical properties Complex ions Coordination number Coordinate bond Polydentate ligands Chelating agents Catalyst Haber process Contact process

Atomic Radii The electron configurations of d-block elements are very similar Small increase of ENC going across period The increase of the 3d electrons shield 4s from interacting with protons Thus, atomic radii is relatively similar across period This explains the ability of metals to form alloys (solutions/mixtures of metals) Atoms of 1 d-block metal can often replace another and still keep the structure

Physical properties All metals High electrical and thermal conductivity High melting point Malleable High tensile strength – hold large loads w/o breaking Ductile Iron, cobalt, and nickel are ferromagnetic Strongest magnetism (discussed section 13.2)

Physical properties explained Metallic bonding (chapter 4) Sea of delocalized electrons Holds metal lattice together Strong metallic bonds High electrical conducivity Small atomic radii Higher density than K and Ca

Definition of transition metal (TM) Elements whose atoms have an incomplete d sub-level shell, or which can form cations with an incomplete d sub-shell. Which elements are not transition metals in the 4th row? Potassium, Calcium, Zinc, Gallium  Krypton Zinc Does not typically form colored compounds Shows only 2+ oxidation state in compounds

Chemical properties In general: Form compounds with more than one oxidation number Form numerous complex ions Form colored compounds Act as catalysts when elements or compounds

Variable oxidation numbers The big jump Ca forms from +2 to +3 means this is energetically unstable Ti is more gradual, so can form +2, +3, +4 then a jump occurs so will not form +5

Variable oxidation numbers Various oxidation states: the ones in blue are the most common

Variable oxidation numbers All TMs have +2 and +3 +3 is more common for early TMs and +2 for later due to the increase in ENC (and electronegativity) Max oxidation state increases +1 until Mn at +7 then decreases -1 This is due to use of 4s and 3d electrons Oxidation states above +3 show covalent character Higher + charge pulls more on the electrons of anion Higher oxid. state tend to be oxidizing agents

Complex ions Coordinate bond also called dative bond A lone pair of electrons is used to form cov. bond High charge density in solution, TM attract H2O molecules (or other molecules/ions with lone pairs of e-) called ligands

Complex ions Number of bonds attached to the central metal ion = coordination number Number and type of ligand can change the color [Cu(H2O)6]2+ + HCl  [Cu(Cl)4]2- + NH3  [Cu(H2O)2(NH3)4]2+

Complex ions

Polydentate ligands – chelating agents Polydentate: able to provide multiple lone pairs for ligand bonding Chelate: complex having at least 1 polydentate ligand EDTA4- can take the place of 6 monodentate ligands Important in foods Binds TM ions To Inhibit oxid. RXNs :

TM and their ions as catalysts Catalyst: increases rate of RXN by lowering activation energy Two types of TM catalysts Homogeneous Heterogeneous

Heterogeneous TM catalysts Heterogeneous catalyst: the catalyst is in a different state from the reactants Haber process: used to produce ammonia Uses Fe solid powder as a catalyst N2(g) + 3H2(g)  2NH3(g) Contact Process: used to produce SO3 for sulfuric acid production V2O5 solid (pellets) used as a catalyst 2SO2(g) + O2(g)  SO3(g) Easily removed via filtration – preferred for industry

Homogeneous TM catalysts Homogeneous catalysts: catalyst is in same state as the reactants Fe2+ in heme for oxygen transport Co3+ in Vitamin B12

Magnetic properties of TMs and their compounds Unpaired electrons can act like small magnets When aligned, these can have a variety of magnetic properties This is determined by placing in an external magnetic field 3 types of magnetism Diamagnetic Paramagnetism Ferromagnetism

Diamagnetism Diamagnetic – property of all materials with weak magnetism Most materials are diamagnetic Orbital motion of electrons produce magnetic fields that oppose external magnetic fields Zinc is diamagnetic (no unpaired e-)

Paramagnetism Occurs with substances which have unpaired electrons and is stronger than diamagnetism Produces magnetization proportional to the applied field (and in the same direction) Is a property of single atoms or ions with unpaired, spinning electrons Increases as number of unpaired e- increases then reaches a max at Cr then decreases

Ferromagnetic Largest effect sometimes producing effects larger than the applied field Occurs when there is a long range ordering of unpaired e- Fe, Co and Ni With many atoms, the large number of unpaired e- can line up in domains Become more ordered when mag. field applied Magnetism remains after field removed