In which of the following actinoid elements 6d subshell is vacant?
Pu, Plutonium
Understanding Actinoid Electron Configurations
Actinoid elements are a series of radioactive elements found in the periodic table, specifically from Actinium (Ac, atomic number 89) to Lawrencium (Lr, atomic number 103). These elements are characterized by the filling of the \( 5f \) electron subshell. However, the electron configurations of actinoids are complex and often show irregularities because the energy levels of the \( 5f \), \( 6d \), and \( 7s \) subshells are very close.
The general electron configuration for actinoids is typically written as \( [Rn] 5f^n 6d^m 7s^2 \), where \( [Rn] \) represents the electron configuration of the noble gas Radon. The values of \( n \) and \( m \) vary across the series. Sometimes, electrons that would typically occupy the \( 6d \) subshell in the gaseous state shift to the \( 5f \) subshell due to relativistic effects and electron-electron repulsion, leading to a \( 6d \) subshell being vacant (meaning \( m=0 \)). We need to examine the electron configurations of the given options to determine which one has a vacant \( 6d \) subshell.
Analyzing Electron Configurations of Given Actinoids
Let's look at the typical ground state electron configurations for the actinoid elements provided in the options:
- Protactinium (Pa), Z=91: The electron configuration for Protactinium is usually given as \( [Rn] 5f^2 6d^1 7s^2 \). In this case, the \( 6d \) subshell is not vacant as it contains one electron.
- Neptunium (Np), Z=93: The electron configuration for Neptunium is often reported as \( [Rn] 5f^4 6d^1 7s^2 \) or \( [Rn] 5f^5 7s^2 \). Using the more common configuration with a \( 6d \) electron, it is not vacant. Even with the second configuration, the question asks for a vacant \( 6d \) subshell among the options, and other options must be considered.
- Lawrencium (Lr), Z=103: Lawrencium is the last element in the actinoid series. Its configuration is often considered to be \( [Rn] 5f^{14} 6d^0 7s^2 \) or \( [Rn] 5f^{14} 7s^2 7p^1 \). In the configuration \( [Rn] 5f^{14} 6d^0 7s^2 \), the \( 6d \) subshell is vacant.
- Plutonium (Pu), Z=94: The electron configuration for Plutonium is typically given as \( [Rn] 5f^6 6d^0 7s^2 \). In this configuration, the \( 6d \) subshell is indeed vacant, as there are zero electrons in it.
Identifying the Actinoid with a Vacant 6d Subshell
Comparing the electron configurations:
- Pa: \( 6d^1 \) (Not vacant)
- Np: \( 6d^1 \) or \( 6d^0 \) (Varies, but often listed with \( 6d^1 \))
- Lr: \( 6d^0 \) (Vacant)
- Pu: \( 6d^0 \) (Vacant)
Both Plutonium (Pu) and typically Lawrencium (Lr) can have a vacant \( 6d \) subshell in their ground state electron configurations. However, among the provided options, Plutonium (Pu) is listed as the correct answer. The configuration \( [Rn] 5f^6 7s^2 \) for Plutonium (Pu, Z=94) clearly shows a vacant \( 6d \) subshell.
Summary of Actinoid Electron Configurations (Selected)
| Element | Symbol | Atomic Number (Z) | Typical Ground State Electron Configuration | 6d Subshell Status |
|---|---|---|---|---|
| Protactinium | Pa | 91 | \( [Rn] 5f^2 6d^1 7s^2 \) | Not Vacant (\( 6d^1 \)) |
| Neptunium | Np | 93 | \( [Rn] 5f^4 6d^1 7s^2 \) or \( [Rn] 5f^5 7s^2 \) | Often Not Vacant (\( 6d^1 \)) |
| Lawrencium | Lr | 103 | \( [Rn] 5f^{14} 6d^0 7s^2 \) or \( [Rn] 5f^{14} 7s^2 7p^1 \) | Vacant (\( 6d^0 \)) |
| Plutonium | Pu | 94 | \( [Rn] 5f^6 6d^0 7s^2 \) | Vacant (\( 6d^0 \)) |
Based on standard electron configurations, Plutonium (Pu) is an actinoid element among the options that has a vacant \( 6d \) subshell.
Revision Table: Actinoid Electron Configurations
| Actinoid | Symbol | Z | Electron Configuration (Focus on 5f, 6d, 7s) | 6d Subshell |
|---|---|---|---|---|
| Protactinium | Pa | 91 | \( ... 5f^2 6d^1 7s^2 \) | \( 6d^1 \) |
| Neptunium | Np | 93 | \( ... 5f^4 6d^1 7s^2 \) or \( ... 5f^5 7s^2 \) | Often \( 6d^1 \) |
| Lawrencium | Lr | 103 | \( ... 5f^{14} 6d^0 7s^2 \) or \( ... 5f^{14} 7s^2 7p^1 \) | \( 6d^0 \) |
| Plutonium | Pu | 94 | \( ... 5f^6 6d^0 7s^2 \) | \( 6d^0 \) |
Additional Information: Complexity of Actinoid Configurations
The electron configurations of actinoids are notoriously difficult to determine precisely, especially for isolated atoms in the gaseous state. The small energy difference between the \( 5f \), \( 6d \), and \( 7s \) orbitals means that multiple configurations can be close in energy, and the observed ground state configuration can be sensitive to various factors. Predicting these configurations accurately requires complex theoretical calculations. For elements like Neptunium (Np), sometimes both \( 5f^4 6d^1 7s^2 \) and \( 5f^5 7s^2 \) are considered valid depending on the context or source. Plutonium (Pu) at Z=94, however, is consistently listed with the \( 5f^6 7s^2 \) configuration, showing a vacant \( 6d \) subshell. Lawrencium (Lr) at Z=103, being the last element, also often shows a filled \( 5f \) subshell and an empty \( 6d \).
These exceptions and irregularities make the study of actinoid chemistry fascinating but challenging.
Important Questions from Electrochemistry
Identify transition metal complexes which are not octahedral in shape.
(A) [Co(NH₃)₆]³⁺
(B) [Ni(CO)₄]
(C) [CoCl(NH₃)₅]²⁺
(D) [CoCl₂(NH₃)₄]⁺
(E) [PtCl₄]²⁻
Choose the correct answer from the options given below:
The product of complete hydrolysis of XeF₆ in the following reaction is:
XeF₆ + H₂O → ? HF
In a reaction A and B react to form product. The initial rate of reaction (ro) was determined using different initial concentrations of A and B as shown below:
A/mol L-1 B/mol L-1 ro/mol L-1 s-1 0.10 0.30 6.81 × 10-4 0.10 0.10 2.27 × 10-4 0.20 0.30 13.62 × 10-4 What is the initial rate of reaction (ro) when the critical concentration of A and B is 0.50 mol/L and 0.50 mol/L, respectively?
Which of the following shows both, Frenkel and Schottky defect?
The role of a catalyst is to change:
