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Transition Elements and Actinoid Properties
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1
Question
Why are d-block transition elements studied separately from non-transition elements?
Answer
Because their partially filled d orbitals lead to unique properties.
2
Question
Which elements belong to the transition metals series?
Answer
Silver, gold, platinum, iron, copper, titanium.
3
Question
What is the electronic configuration pattern of outer orbitals in transition elements?
Answer
(n-1)d and ns, with exceptions like Pd.
4
Question
Why do Cr and Cu have unexpected electron configurations?
Answer
Small energy difference between 3d and 4s orbitals causes stability in half-filled and filled sets.
5
Question
What is the general physical nature of transition metals?
Answer
Metallic, high tensile strength, ductile, malleable, high conductivity, lustrous.
6
Question
How do melting points vary across transition metals?
Answer
They rise to a maximum mid-series and then fall as atomic number increases.
7
Question
What causes high melting points in transition metals?
Answer
Involvement of d electrons in bonding.
8
Question
Why do transition metals show variable oxidation states?
Answer
Due to incomplete filling of d orbitals allowing sharing or loss of d electrons.
9
Question
What trend is observed in ionic radii of transition metal ions of same charge across a series?
Answer
Decreases with increasing atomic number due to successive addition of electrons to d orbitals.
10
Question
How does lanthanoid contraction affect the properties of 5d series elements?
Answer
Comparable radii of 4d and 5d elements due to filling of 4f orbitals.
11
Question
What is the trend in atomic radii from 3d to 4d and 5d series?
Answer
Increase from 3d to 4d, then similar in 4d and 5d series due to lanthanoid contraction.
12
Question
Why do transition elements exhibit high enthalpy of atomization?
Answer
Large number of unpaired electrons lead to strong interatomic bonds.
13
Question
What causes the decrease in atomic radii along a series of transition metals?
Answer
Increasing nuclear charge with a small shielding effect of d electrons.
14
Question
What is the effect of multiple oxidation states of transition metals on their chemistry?
Answer
They can participate in varying redox reactions, forming diverse compounds.
15
Question
Why do transition metals form coloured ions?
Answer
Partially filled d orbitals allow d-d electronic transitions that absorb visible light.
16
Question
Explain the trend of ionisation enthalpy in 3d series.
Answer
It generally increases across the series but shows irregularities due to electron shielding and stability of configurations.
17
Question
What is the significance of exchange energy in transition metals?
Answer
It stabilizes certain electronic configurations, affecting ionisation energy and magnetic properties.
18
Question
What property explains why Mn and Co are the strongest oxidising agents among the first-row transition metals?
Answer
Their high positive standard reduction potentials.
19
Question
Why do highest oxidation states of metals generally appear in oxides or fluorides?
Answer
These compounds stabilize metals in their highest oxidation states.
20
Question
Which is a stronger reducing agent: Cr or Fe? Why?
Answer
Fe, because it has a more negative E° value.
21
Question
What causes paramagnetism in transition metal complexes?
Answer
Presence of unpaired electrons.
22
Question
How is magnetic moment calculated for first-row transition metal ions?
Answer
Using the ‘spin-only’ formula: μ = √(n(n+2)).
23
Question
What determines the color of transition metal ions in aqueous solution?
Answer
The energy of d-d electronic transitions influenced by ligand nature.
24
Question
Why is the 3+ oxidation state predominant in lanthanoids?
Answer
Stability of the 4fⁿ configuration and ionic size.
25
Question
What is lanthanoid contraction and its consequence?
Answer
Gradual decrease in radii across the series; causes similar sizes of Zr and Hf.
26
Question
Why do actinoids show a wider range of oxidation states than lanthanoids?
Answer
Because 5f, 6d, and 7s levels have similar energies.
27
Question
What property of interstitial compounds distinguishes them from typical ionic or covalent compounds?
Answer
They contain small atoms trapped within metal lattices and are very hard.
28
Question
What is a typical application of lanthanoid oxides?
Answer
Used as phosphors in display screens.
29
Question
In the context of transition metals, what is disproportionation?
Answer
When a substance's oxidation state becomes unstable and converts into lower and higher states.
30
Question
Why is Cu²⁺ instability in aqueous solutions?
Answer
It readily undergoes reduction to Cu⁺ or metallic copper.