28. transition metals
暂无描述。系统推荐的高质量记忆内容，适合每天坚持背诵学习。
卡片预览 (24 张)
Define a transition element.
A “transition element” is an element that forms at least one ion with a partially filled d-subshell.
Why is zinc not classified as a transition element?
Zn forms Zn²⁺ with electron configuration 3d¹⁰; the d-subshell is completely filled, not partially filled.
State the general electronic configuration of a first-row transition element.
[Ar] 3dⁿ 4s², although exceptions occur and ions lose 4s electrons first.
Why do transition metals have variable oxidation states?
The 3d and 4s orbitals have similar energies, so different numbers of electrons can be removed or shared.
Why do transition metals form coloured compounds?
Partially filled d-orbitals allow “d–d transitions” that absorb specific wavelengths of visible light.
What causes the colour observed in a transition-metal complex?
Colour arises because some visible light is absorbed for electron promotion between split d-orbitals; the complementary colour is observed.
Why are many transition metals effective catalysts?
They can change oxidation state easily and provide alternative reaction pathways with lower activation energy.
Why do transition metals form complex ions?
Their small, highly charged ions can accept lone pairs from ligands to form coordinate bonds.
What is a ligand?
A “ligand” is an ion or molecule that donates a lone pair of electrons to a central metal ion.
What is a coordinate bond?
A covalent bond in which both bonding electrons are supplied by one atom.
Name common ligands in transition-metal chemistry.
H₂O, NH₃, Cl⁻, CN⁻ and OH⁻ are common ligands.
What is the coordination number?
The number of coordinate bonds formed between ligands and the central metal ion.
What is the coordination number of [Cu(H₂O)₆]²⁺?
6
Describe the shape of most six-coordinate complexes.
Usually “octahedral”.
Describe the shape of most four-coordinate complexes.
Usually “tetrahedral”, though some may be square planar.
What is meant by a complex ion?
A charged species consisting of a central metal ion surrounded by ligands joined by coordinate bonds.
State the oxidation state of iron in [Fe(H₂O)₆]³⁺.
3
State the oxidation state of copper in [Cu(NH₃)₄(H₂O)₂]²⁺.
2
What is meant by a precipitation reaction in transition-metal chemistry?
Formation of an insoluble hydroxide or other compound from aqueous ions.
What colour is [Cu(H₂O)₆]²⁺ in solution?
Pale blue.
What colour is [Fe(H₂O)₆]²⁺ in solution?
Pale green.
What colour is [Fe(H₂O)₆]³⁺ in solution?
Yellow to violet; commonly described as yellow-brown.
What colour is [Cr(H₂O)₆]³⁺ in solution?
Green or violet depending on conditions.
What colour is [Mn(H₂O)₆]²⁺ in solution?
Very pale pink.