Element guide
Electron configuration of Rhodium (Rh)
The electron configuration of Rhodium is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d8 5s1. In shorthand form it is written as [Kr] 4d8 5s1.
Use this page to connect the notation with atomic number 45, the d-block, and the valence pattern 4d8 5s1.
How to write the configuration
Configuration at a glance
Rhodium has atomic number 45, so a neutral atom has 45 electrons. The configuration 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d8 5s1 is a compact record of where those electrons sit by subshell.
The shorthand [Kr] 4d8 5s1 replaces the filled inner core with the previous noble gas. That notation keeps attention on the electrons that usually explain bonding, ions, and periodic trends.
The Rhodium exception
Based on the Aufbau principle, Rhodium might be expected to follow the pattern of its lighter congener Cobalt (Co: [Ar] 3d7 4s2), giving [Kr] 4d7 5s2. However, Rhodium's ground state is [Kr] 4d8 5s1. One electron from the 5s subshell moves to the 4d subshell to achieve a configuration with lower overall energy.
This exception is less dramatic than the Cr/Mo half-filled d-subshell case, but it occurs because the energy gap between the 4d and 5s orbitals is relatively small in period 5 transition metals. Rhodium is one of several period 5 elements (along with Nb, Mo, Ru, Pd, and Ag) that show this kind of s-to-d electron promotion.
Step-by-step filling walkthrough: 1. Start with atomic number 45. 2. Fill through krypton: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 (36 electrons). 3. Fill 5s2 (38 electrons). 4. Fill 4d7 (45 electrons) naively. 5. For the correct ground state: shift one 5s electron to 4d, producing 4d8 5s1. 6. Verify: add every superscript and confirm the total equals 45.
Common mistakes
The first mistake is writing [Kr] 4d7 5s2 instead of [Kr] 4d8 5s1. Rhodium is one of the period 5 metals that commonly tests your knowledge of Aufbau exceptions. The second mistake is forgetting to verify the total electron count (45).
A third error is confusing Rh with its neighbor Ruthenium (Ru: [Kr] 4d7 5s1) or Palladium (Pd: [Kr] 4d10). Each period 5 element in this block has its own unique exception pattern.
Rhodium reference table
| Item | Value |
|---|---|
| Atomic number | 45 |
| Full configuration | 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d8 5s1 |
| Noble-gas notation | [Kr] 4d8 5s1 |
| Valence clue | 4d8 5s1 |
| Block | d-block |
Use the table as a learning reference, then verify advanced oxidation-state questions with your course material.
Before you submit an answer
- The superscripts add up to 45 for a neutral Rhodium atom.
- The notation follows the filling order used in your course.
- The last occupied subshell matches the periodic-table block.
- Any transition-metal or actinide exception is checked against a reference.
- The shorthand core is a noble gas, not a random previous element.
Common questions
What is the electron configuration of Rhodium?
The neutral Rhodium atom is written as 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d8 5s1. The shorthand form is [Kr] 4d8 5s1.
Is Rhodium an exception to the Aufbau principle?
Yes. The expected configuration following the Cobalt pattern would be [Kr] 4d7 5s2, but the ground state is [Kr] 4d8 5s1 due to the narrow 4d-5s energy gap.
How many valence electrons does Rhodium have?
Start from the outer-shell clue 4d8 5s1. For transition metals, inspect both s and d electrons carefully. Rhodium has 9 valence electrons.
What are the common oxidation states of Rhodium?
Rhodium most commonly exhibits the +3 oxidation state, though +1, +2, and +4 are also known. Its 4d8 5s1 configuration supports a rich coordination chemistry.
Practice nearby concepts
Study notes and practice checks
From answer to understanding
Rhodium is a precious metal used mainly in catalytic converters. Its 4d8 5s1 configuration gives it unique catalytic properties, particularly for breaking chemical bonds.
Practice comparison
Compare Rhodium (Rh) with Cobalt (Co) and Iridium (Ir). Co: [Ar] 3d7 4s2, Rh: [Kr] 4d8 5s1, Ir: [Xe] 4f14 5d7 6s2. Note that Cobalt follows the expected d7 s2 pattern, Rhodium has the d8 s1 exception, and Iridium reverts to d7 s2 — a good example of period 5 exceptions not extending to period 6.
Teacher and self-study notes
Period 5 transition metals (especially Nb through Ag) commonly show s-to-d electron promotions. The trend is linked to the decreasing 5s orbital energy as nuclear charge increases, making it favorable to pair d electrons rather than leave the 5s orbital occupied.
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