Chapter 4: Problem 119
Some of the following sets of quantum numbers are correct for a \(4 \mathrm{~d}\) electron. Which are correct sets ? (a) \(4,3,2,+\frac{1}{2}\) (b) \(4,2,1,0\) (c) \(4,2,-2,+\frac{1}{2}\) (d) \(4,2,1,-\frac{1}{2}\)
Short Answer
Expert verified
Options (c) and (d) are correct sets for a 4d electron.
Step by step solution
01
Understand Electron Quantum Numbers
Quantum numbers describe the properties of an electron in an atom. There are four quantum numbers:
- Principal quantum number (
"): Indicates the energy level/shell and can have positive integer values (e.g., 1, 2, 3, ...).
- Azimuthal quantum number (
"): Denotes the subshell shape (s, p, d, f, ...) and ranges from 0 to (n-1).
- Magnetic quantum number (
"): Represents the orientation of the orbital and ranges from -
").
- Spin quantum number (
"): Represents the electron's spin and can be
" or -
".
02
Identify 4d Subshell Conditions
For a 4d electron, the principal quantum number
" = 4, and the azimuthal quantum number
" = 2 (where d corresponds to
"). The possible magnetic quantum number values for d orbitals range from -2 to +2 (
"). The electron spin quantum number (
") can be either +
" or -
".
03
Evaluate Option (a)
The given set is 4, 3, 2, +½:
-
" = 4 is correct as it corresponds to the 4th energy level.
-
" = 3 is incorrect since it does not correspond to the d subshell (should be
").
Therefore, this set is incorrect for a 4d electron.
04
Evaluate Option (b)
The given set is 4, 2, 1, 0:
-
" = 4 is correct for the 4th energy level.
-
" = 2 is correct for a d subshell.
-
" = 1 is within the correct range for a d orbital.
-
" = 0 is incorrect for an electron's spin; it must be +½ or -½.
Thus, this set is incorrect for a 4d electron.
05
Evaluate Option (c)
The given set is 4, 2, -2, +½:
-
" = 4 is correct.
-
" = 2 is correct for a d subshell.
-
" = -2 is within the range for d orbitals.
-
" = +½ is a valid spin.
This set correctly represents a 4d electron.
06
Evaluate Option (d)
The given set is 4, 2, 1, -½:
-
" = 4 is correct.
-
" = 2 is correct for a d subshell.
-
" = 1 is within the range for d orbitals.
-
" = -½ is a valid electron spin.
This set also correctly represents a 4d electron.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Principal Quantum Number
The principal quantum number, often symbolized as \( n \), serves as the foundational quantum number in the hierarchy. It essentially tells us about the electron's energy level in an atom, similar to the rung of a ladder. The higher the value, the higher the energy level and the farther it is from the nucleus.
Here's a breakdown of its characteristics:
Here's a breakdown of its characteristics:
- It has positive integer values: \( n = 1, 2, 3, \ldots \).
- As \( n \) increases, the atomic radius typically increases, meaning electrons in higher energy levels are found further from the nucleus.
- It dictates the size of the orbital – larger \( n \) values mean larger orbitals.
Azimuthal Quantum Number
The azimuthal quantum number, represented by \( l \), is key to defining an electron's subshell or sublevel. It provides insight into the shape of the orbital where the electron is likely to be found. The value of \( l \) depends on the principal quantum number \( n \) and can range from 0 to \( n-1 \).
A concise explanation includes:
A concise explanation includes:
- For \( n = 4 \), \( l \) can be 0, 1, 2, or 3. These correspond to the s, p, d, and f subshells, respectively.
- Each value of \( l \) determines a specific shape: \( l = 0 \) is spherical (s), \( l = 1 \) is dumbbell-shaped (p), \( l = 2 \) has a double dumbbell shape (d), and so on.
- The azimuthal quantum number also informs us about the angular momentum of an electron within that subshell.
Magnetic Quantum Number
The magnetic quantum number, designated as \( m_l \), delves deeper into the orientation of an electron's orbital within a subshell. It arises due to the magnetic field effects, which influence how these orbitals align naturally.
Critical points about \( m_l \) include:
Critical points about \( m_l \) include:
- For every azimuthal quantum number \( l \), the magnetic quantum number \( m_l \) can vary from \( -l \) to \( +l \), including zero. For instance, if \( l = 2 \) (d orbital), \( m_l \) can be -2, -1, 0, +1, or +2.
- This number determines the number of orientations an orbital can have within a subshell.
- An electron's specific \( m_l \) value dictates the precise shape and orientation of its orbital, which is integral for complex structures like multi-electron systems.
Spin Quantum Number
The spin quantum number, noted as \( m_s \), brings us into the realm of an electron's intrinsic spin, a fundamental property akin to angular momentum. This quantum number distinguishes electrons even further by indicating their specific spin direction within an orbital.
Key aspects to consider:
Key aspects to consider:
- It can take one of two possible values: \( +\frac{1}{2} \) or \( -\frac{1}{2} \).
- This property allows electrons to pair within an orbital, each having opposite spins, contributing to the stability of atoms.
- The spin states are critical in defining phenomena like magnetism, as aligned spins generate a magnetic moment.