13.1 First-row d-block elements

Electron Configuration

Similar properties due to small range in atomic radii.

To understand atomic radii must consider electron configuration.

Unusual electron configuration of Chromium and Copper due to 1/2 filled and filled 3 d sub-levels.

Small decrease in atomic radii across d- block= due to small increase in effective nuclear charge felt by outer 4s electrons.

Similarity in atomic radii= ability of transition metals to form alloys.

Small increase in effective nuclear charge= small range of first ionization energies

Physical Properties

-High electrical and thermal conductivity

-High melting point

-Malleable

-High tensile strength (hold large loads without breaking)

-Ductile

Properties explained by: strong metallic bonds.

Chemical Properties

-Form compounds with more than one oxidation number

-Form a variety of complex ions

-Form colored compounds

-Act as a catalyst when they are either elements or compounds

Zinc is not a Transition Metal

Doesn't comply with characteristics; only has one oxidation number (2+).

Reason: electron configuration; d sub-level is complete

Explanation of variable oxidation number of transition elements

-Transition metals have a wide range of oxidation numbers as opposed to s- block elements, that have only one.

-All transition metals have +2 and +3 oxidation states.

- Oxidation state of elements increases by +1 and reaches maximum at Manganese, then decreases by -1.

- Oxidation states above +3 usually have covalent character; have higher charge density so they polarize negative ion and increase covalent character.

-Compounds with higher oxidation states may be oxidizing agents (accept electrons from other atoms) Example: use Potassium dichrotomate (VI) in oxidation of alcohol.

Catalyst: substance that alters rate of reaction (lowers activation energy)

Chemical industry-economical alternatives

Heterogeneous catalysts: catalysts are in different state from the reactants. Transition metals use 3d and 4s electrons to form bonds to reactant molecules

Catalyst can be removed by filtration after use

Homogenous catalysts: catalysts are in same state of matter as the reactants.

Ability to show several oxidation states

Work in the human body

Fertilizers, drugs, plastics, explosives

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13.1 First-row d-block elements

Complex ions

Transition metal ions have high charge density (small, high effective nuclear charge), attract water molecules and form bonds with positive ions forming complex ions.

Formed when central ion is surrounded by molecules/ions with lone pairs of electrons. Ligands are attached via coordinate bonds.

Ligands have one atom with a lone pair of electrons, which are used to form the coordinate bond

# of coordinate bonds from ligands to central ion is the coordination number.

In aqueous solutions, water molecules generally are ligands, but they can be replaced (ligand exchange)

Some species have more than 1 available lone pair to form coordinate bonds (polydentate ligands)

EDTA4- has 6 atoms with lone pairs available= six monodentate ligands (hexadentate ligand)

Grip central ion in a six prolonged claw called a chelate, a complex containing at least one polydentate ligand

EDTA4- food additive that removes transition ions from solution and inhibits oxidation reactions

Transition metals and ions as catalysts

Carry oxygen through the bloodstream. Broken when oxygen needs to be released.

Magnetic properties of transition metals

Electrons can behave as magnets

Opposite spins=no net magnetic effect

Some transition elements have unpaired electrons, leading to magnetic properties

Classification:

Diamagnetism: weak opposition to magnetic field

Paramagnetism: unpaired electrons, stronger than diamagnetism. Magnetization proportional to applied field in same direction

Ferromagnetism: largest effect, produces magnetization greater than applied field. Long range ordering of unpaired electrons

Most materials are diamagnetic

Iron, cobalt, nickel –ferromagnetic

Unpaired d electrons have parallel spins in domains. Become more ordered when exposed to external magnetic field

Magnetism remains after external magnetic field is removed

Transition metals show paramagnetic properties

Paramagnetism increases w/ number of unpaired electrons (from left to right) Zinc has no unpaired electrons (diamagnetic)