General Electronic Configuration and Exceptions in d-Block Elements
The Electronic Configuration of D Block Elements is essential for JEE Main Chemistry. Understanding how electrons are arranged in the d orbitals explains the diverse properties and reactivity of transition metals. These elements exhibit unique behavior—variable oxidation states, colored compounds, and special magnetic and catalytic traits—because of their characteristic d-electron arrangements. Mastering the electron configuration patterns and recognising key exceptions enables students to tackle configuration-based questions and link structure with periodic trends confidently.
General Electronic Configuration Of D Block Elements
D block elements are positioned in the centre of the periodic table, from groups 3 to 12. They are sometimes called transition elements and have electrons progressively added to the (n−1)d orbitals while the outermost shell is usually ns. The general electronic configuration of d block elements is (n–1)d1–10ns0–2. Here, "n" is the principal quantum number for the s orbital one period ahead of the d subshell. This overall electron arrangement governs physical and chemical properties for the entire d block.
| Block | General Configuration | Start & End Group | Typical Series |
|---|---|---|---|
| d-block | (n–1)d1–10ns0–2 | Group 3 → Group 12 | 3d, 4d, 5d, 6d |
For example, Scandium (Sc, Z=21): [Ar] 3d14s2. The 3d, 4d, and 5d series all follow similar filling patterns with some anomalies caused by specific subshell stabilities.
d-Block Series: 3d, 4d, 5d and Exceptions
The d block has four series, each representing progressive filling of a distinct (n–1)d orbital set:
- 3d series (Period 4): Sc (21) to Zn (30) — [Ar] 3d1–104s0–2
- 4d series (Period 5): Y (39) to Cd (48) — [Kr] 4d1–105s0–2
- 5d series (Period 6): La/Hf (57/72) to Hg (80) — [Xe] 4f145d1–106s0–2
- 6d series (Period 7, incomplete): Ac (89) onwards — [Rn] 5f146d1–107s0–2
Some elements display exceptional configurations due to stability of half-filled (d5) and fully filled (d10) d subshells. For example:
- Chromium (Cr, Z=24): [Ar] 3d54s1 (not 3d44s2)
- Copper (Cu, Z=29): [Ar] 3d104s1 (not 3d94s2)
- Niobium (Nb, Z=41) and Molybdenum (Mo, Z=42) in 4d series also deviate for similar reasons.
| Element | Atomic No. | Electronic Configuration (abbreviated) | Type |
|---|---|---|---|
| Fe | 26 | [Ar] 3d64s2 | 3d series, regular |
| Cr | 24 | [Ar] 3d54s1 | 3d, exception |
| Cu | 29 | [Ar] 3d104s1 | 3d, exception |
| Pd | 46 | [Kr] 4d105s0 | 4d, exception |
Learn to spot these exceptions—they are frequent in JEE questions! Practise using the Aufbau principle and revise d and s orbital energies for each period.
Trends & Properties Linked to D Block Electronic Configurations
Transition elements exhibit unique properties, explained by their electronic configurations:
- Variable oxidation states because energies of ns and (n–1)d electrons are similar, so both can be lost.
- Formation of colored compounds due to d–d electron transitions; only possible when d orbitals are partially filled.
- Paramagnetism when unpaired d electrons are present; magnetic moment μ = √n(n+2) BM, where n = unpaired electrons.
- Catalytic activity: empty d orbitals allow adsorption of reactants and formation of intermediates.
- High melting and boiling points, and ability to form strong metallic bonds.
Elements with fully filled d10 configurations (Zn, Cd, Hg) show less typical transition behavior—no variable oxidation states, no colored ions, diamagnetic in nature. Alloys, interstitial compounds, and complex formation are also common thanks to similar atomic radii and availability of d orbitals.
Examples and JEE Practice Problems
Let’s see step-by-step approaches for common configurations:
- Iron (Fe, Z=26): 1s22s22p63s23p63d64s2 (or [Ar] 3d64s2)
- Fe2+ ion: Remove 4s electrons first: [Ar] 3d6
- Write configuration for Mo (Z=42): [Kr] 4d55s1 (exceptional)
- Spotting exceptions—if d4 or d9, check if “borrowing” an s electron gives d5 or d10 (stabilization!)
Common pitfall: Always remove ns electrons before (n–1)d when forming cations; for example, Fe3+ is [Ar] 3d5, not [Ar] 3d34s2.
Tabular Summary: 3d, 4d, and 5d Series Electronic Configurations
| Element | Abbreviated Config. | Notes |
|---|---|---|
| Sc (21) | [Ar] 3d14s2 | Regular |
| Cr (24) | [Ar] 3d54s1 | Exception |
| Cu (29) | [Ar] 3d104s1 | Exception |
| Zn (30) | [Ar] 3d104s2 | Fully filled d block |
| Mo (42) | [Kr] 4d55s1 | Exception |
| Ag (47) | [Kr] 4d105s1 | Exception |
| Pd (46) | [Kr] 4d10 | Unique (no 5s) |
Refer to electronic configuration tables for all d block elements when revising. For deeper understanding of periodicity and group trends, explore periodic table mock tests or classification of elements pages.
Properties of D Block: Color, Magnetism, and Catalysis
Why are many d block compounds colored? When d orbitals are partly filled, visible light promotes “d–d” transitions. The color observed is the complement of the color absorbed.
Magnetic behavior follows from unpaired electrons: more unpaired electrons in d orbitals mean stronger paramagnetism. Mn2+ (d5): strongly paramagnetic; Zn2+ (d10, all paired): diamagnetic.
- Only ions with d1 to d9 are colored; d0 and d10 are usually colorless.
- Number of unpaired d electrons determines magnetic moment (μ):
μ = √n(n+2) Bohr Magnetons (BM) - Most d block elements are effective catalysts, exploiting variable oxidation states and vacant d orbitals for reaction intermediates.
If you want to deepen your grasp of magnetic and electronic behavior, see the magnetic properties of d block or coordination compounds pages for advanced examples.
Tips and Tricks for D Block Configuration Questions
- Always apply the Aufbau principle, but double check for d5 & d10 stabilization exceptions.
- When forming cations, remove ns electrons before (n–1)d electrons.
- Memorize the key exception elements—commonly tested in configuration MCQs.
- Review periodic trends: 5d > 4d > 3d in atomic/ionic size, but melting points and color trends are non-linear.
- Connect configuration to property: if d shell is completely filled or empty = colorless, diamagnetic.
- For rapid revision, summarise a chart of atomic number, symbol, series, and configuration.
- Reinforce practice with lanthanide and actinide contrasts.
Consistent revision with properly structured tables and MCQ drills will greatly boost your speed and accuracy when tackling d block elements questions in JEE Main.
Explore More JEE Chemistry D Block Resources
- Test configuration mastery with d and f block mock papers.
- Understand periodicity using atom vs ion patterns and d block revision notes.
- Learn about coordination compounds and their use of d orbitals.
- Explore d block properties, transition characteristics, and more.
- Broaden perspective with p block vs d block comparisons for comprehensive mastery.
Practise configuration writing, brush up on exception trends, and make the Electronic Configuration of D Block Elements your scoring advantage in JEE Main. For expert-guided learning and more resources, Vedantu remains a trusted companion in competitive Chemistry preparation.
FAQs on Electronic Configurations of d-Block Elements
1. What is the electronic configuration of d-block elements?
The electronic configuration of d-block elements follows the general form “(n-1)d1-10ns0-2”, meaning electrons fill the d orbitals after the ns orbital is filled.
Key points:
- D-block elements are located in groups 3 to 12 of the periodic table.
- They include the 3d, 4d, and 5d transition series.
- Electrons fill the (n-1)d subshell after the ns subshell, but exceptions exist for stability (e.g. Cr, Cu).
2. What is the general electronic configuration of d-block metals?
D-block metals follow the general electronic configuration: (n-1)d1-10ns0-2.
Summary:
- For 3d series: n = 4; for 4d: n = 5; for 5d: n = 6
- Examples:
- Scandium (Sc): [Ar] 3d14s2
- Iron (Fe): [Ar] 3d64s2
- This arrangement explains their chemical and physical properties, including variable oxidation states and magnetism.
3. Which elements are included in the 3d, 4d, and 5d series of the d-block?
The d-block is split into three main series based on principal quantum numbers:
- 3d Series (Period 4): Scandium (Sc) to Zinc (Zn)
- 4d Series (Period 5): Yttrium (Y) to Cadmium (Cd)
- 5d Series (Period 6): Lanthanum (La), Hafnium (Hf) to Mercury (Hg)
4. Why do d-block elements show variable oxidation states?
D-block elements exhibit variable oxidation states due to the similar energy levels of their (n-1)d and ns electrons, allowing both to participate in bonding.
- Electrons from both the outer ns and penultimate (n-1)d orbitals are available for bond formation.
- This flexibility results in multiple possible oxidation states for many transition elements (e.g., Fe2+ and Fe3+).
- The highest oxidation state generally increases from Sc to Mn, then decreases toward Zn.
5. What is the electron configuration of the element 1s2 2s2 2p6 3s2 3p6 3d6 4s2?
The configuration 1s2 2s2 2p6 3s2 3p6 3d6 4s2 belongs to iron (Fe), atomic number 26.
Key points:
- Configuration: [Ar] 3d6 4s2
- Iron is a 3d series d-block element with variable oxidation states (+2, +3).
- Its electron arrangement explains its magnetism and catalytic properties.
6. Why do some d-block elements deviate from the regular Aufbau filling order?
Certain d-block elements, such as chromium (Cr) and copper (Cu), show exceptions to the Aufbau principle for extra stability.
- Half-filled (d5) and fully-filled (d10) d-subshells are energetically more stable.
- Example: Cr is [Ar] 3d54s1 (not 3d44s2), and Cu is [Ar] 3d104s1 (not 3d94s2).
- This effect is called configuration anomaly.
7. What properties of d-block elements are influenced by their electronic configuration?
The electronic configuration of d-block elements is directly related to their key properties:
- Variable oxidation states (– due to ns and (n-1)d electrons' similar energies)
- Color of compounds (– unpaired d electrons can absorb visible light via d-d transitions)
- Magnetic behavior (– unpaired electrons cause paramagnetism or ferromagnetism)
- Catalytic activity (– variable valency and ability to form complexes)
8. How do you write the electronic configuration of Fe?
The electronic configuration of iron (Fe, atomic number 26) is:
- 1s2 2s2 2p6 3s2 3p6 4s2 3d6
- Condensed form: [Ar] 3d6 4s2
- In Fe2+ and Fe3+ ions, electrons are removed first from 4s, then 3d.
9. Where can I download the electronic configuration table for d-block elements?
You can find electronic configuration tables or PDFs for all d-block elements on educational websites and exam preparation portals.
- They provide quick reference for 3d, 4d, 5d series elements.
- These tables help in revision for JEE, NEET, and CBSE exams.
- Typically available as downloadable PDF charts summarising all transition metals' configurations.
10. Is there a difference between transition elements and d-block elements?
While all transition elements are part of the d-block, not all d-block elements are considered transition elements.
- Transition elements: Elements with partially filled d-orbitals in their atoms or ions (e.g., Sc to Zn).
- Some d-block elements, like Zn, Cd, Hg, have completely filled d-subshells and are often termed 'd-block' but not 'transition elements' by strict IUPAC definition.
- The distinction is important for exam questions and classification in the periodic table.
11. How is the color of d-block compounds related to their electronic configuration?
The color of d-block compounds is due to electronic transitions between d-orbitals (d-d transitions).
- Unpaired electrons in partially filled d-orbitals absorb certain wavelengths of visible light, causing colors.
- The specific color depends on the metal ion's configuration, ligand field, and oxidation state.
- For example, Cu2+ compounds are blue, and Cr3+ compounds are green or violet.
