# Hund's Rule for Determining Term Symbol Energy Order

• Mr_Allod
In summary, the experts suggest that Hund's rules only apply to equivalent electrons and may be iffy when applied to configurations with two orbitals such as p^5d^1 or d^9f^1. In these cases, it is best to consider the subshell as more than half-filled.
Mr_Allod
Homework Statement
Use Hund's rules to determine the energy order of the term symbols of a ##d^9f^1## electron configuration.
Relevant Equations
None
Hello there, for the above question I have no issue finding the term symbols but I am a little unsure about employing Hund's rules to the electron configuration, particularly those referring to the energies based on the total angular momentum J. These state:

- In a less than ##\frac12##-filled subshell Lowest J-value is Lowest energy
- In a more than ##\frac12##-filled subshell Highest J-value is Lowest energy

For configurations where only one orbital is involved such as ##p^5,d^3## etc. this is easy to apply. But what about configurations where two orbitals are involved such as ##p^5d^1## or ##d^9f^1##? In these cases to which orbital do we apply the less/more than ##\frac 12##-filled condition?

Hund's rules apply only to equivalent electrons. It would work for d9, but applying it to d9f1 is iffy.

In any case, considering that this is the problem you were given, the equivalent electrons being the d9, I would consider the subshell as more than half-filled.

DrClaude said:
Hund's rules apply only to equivalent electrons. It would work for d9, but applying it to d9f1 is iffy.

In any case, considering that this is the problem you were given, the equivalent electrons being the d9, I would consider the subshell as more than half-filled.
Thank you for the answer, I've had a very hard time finding a straight answer to this question anywhere so it's nice to have something to go on.

## 1. What is Hund's Rule for Determining Term Symbol Energy Order?

Hund's Rule is a principle in quantum mechanics that states that for atoms with multiple electrons, the lowest energy state is achieved when the electrons are distributed in a way that maximizes the total spin of the system.

## 2. How does Hund's Rule apply to electron configurations?

Hund's Rule applies to electron configurations by determining the order in which electrons fill orbitals. It states that electrons will first fill each orbital with one spin before pairing up.

## 3. How does Hund's Rule affect the stability of an atom?

Hund's Rule affects the stability of an atom by ensuring that the electrons are distributed in a way that minimizes the overall energy of the system. This leads to a more stable and lower energy state for the atom.

## 4. What is the significance of Hund's Rule in chemistry?

Hund's Rule is significant in chemistry because it helps to predict the electron configuration and properties of atoms. It also plays a role in determining the reactivity and bonding behavior of elements.

## 5. Are there any exceptions to Hund's Rule?

Yes, there are some exceptions to Hund's Rule, particularly in transition metals. In some cases, the energy required to pair electrons in an orbital may be lower than the energy gained by maximizing spin. Additionally, the presence of repulsive forces can also lead to deviations from Hund's Rule.

Replies
5
Views
2K
Replies
1
Views
1K
Replies
2
Views
2K
• Atomic and Condensed Matter
Replies
3
Views
2K
Replies
7
Views
5K
Replies
5
Views
3K
Replies
4
Views
8K
• Chemistry
Replies
1
Views
293
• Quantum Physics
Replies
3
Views
1K
• Atomic and Condensed Matter
Replies
8
Views
3K