---
title: "Transition elements; first series configuration"
subject: "Engineering Chemistry"
chapter: 5
key: "semester_2/engineering_chemistry:why-transition-elements-typical"
source: https://www.bctengineer.com/q/semester_2/engineering_chemistry/why-transition-elements-typical
site: BCT Engineering
---

# Transition elements; first series configuration

Engineering Chemistry · Chapter 5: 3-d Transition Elements and their Applications

- Asked in: 2074 Bhadra, 1+1+3 marks
- Video: [First Row d-Block Transition Elements](https://www.youtube.com/watch?v=AoJyOLQrsBU) — Science with Dr. Johnson
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_2/engineering_chemistry/why-transition-elements-typical
- Whole chapter: https://www.bctengineer.com/md/semester_2/engineering_chemistry/chapter-5

## Question

What are transition elements? Why are all the transition elements not considered as typical transition elements? Explain the electronic configuration of the first transition elements.

## Short answer

Transition elements have an incomplete d subshell in the atom or common ion. Zn, Cd, Hg are not typical because they have a filled d10 configuration in both, lacking variable oxidation states, colour, and paramagnetism. First row configurations: Sc [Ar]3d1 4s2, Ti 3d2 4s2, V 3d3 4s2, Cr 3d5 4s1, Mn 3d5 4s2, Fe 3d6 4s2, Co 3d7 4s2, Ni 3d8 4s2, Cu 3d10 4s1, Zn 3d10 4s2.

## Answer

#### Transition elements
Elements which have an incompletely filled d subshell either in the atom or in any of their common oxidation states are called transition elements (d-block elements lying between s- and p-blocks). Examples: Ti, V, Cr, Mn, Fe, Co, Ni, Cu.

#### Why not all are typical
Zn, Cd and Hg have a completely filled d¹⁰ subshell in the atom and in their common oxidation state (+2), so they do not show the typical properties of transition elements: variable oxidation states, coloured ions, paramagnetism, complex formation and catalytic activity. They are not considered typical transition elements.

#### Electronic configuration of the first transition series
| Element | Z | Configuration |
|---|---|---|
| Sc | 21 | [Ar] 3d¹ 4s² |
| Ti | 22 | [Ar] 3d² 4s² |
| V | 23 | [Ar] 3d³ 4s² |
| Cr | 24 | [Ar] 3d⁵ 4s¹ (exception) |
| Mn | 25 | [Ar] 3d⁵ 4s² |
| Fe | 26 | [Ar] 3d⁶ 4s² |
| Co | 27 | [Ar] 3d⁷ 4s² |
| Ni | 28 | [Ar] 3d⁸ 4s² |
| Cu | 29 | [Ar] 3d¹⁰ 4s¹ (exception) |
| Zn | 30 | [Ar] 3d¹⁰ 4s² |

The exceptions Cr and Cu arise because half-filled (d⁵) and fully filled (d¹⁰) subshells have extra stability (exchange energy and symmetry). General formula: (n−1)d¹⁻¹⁰ ns¹⁻².

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. A transition element has
   A. A full d subshell always
   B. No d electrons
   C. Only s electrons
   D. An incompletely filled d subshell in the atom or common ion
   Answer: D. This is the definition. (Key point: Definition)

2. Why are Zn, Cd, Hg not typical?
   A. d10 in the atom and in +2 state
   B. d5 configuration
   C. No s electrons
   D. They are radioactive
   Answer: A. No variable states, colour or paramagnetism. (Key point: Not typical)

3. Why does Cr have 3d5 4s1?
   A. It has fewer electrons
   B. Half-filled d5 has extra stability
   C. 4s is always empty
   D. It is a noble gas
   Answer: B. Exchange energy and symmetry stabilise d5 and d10. (Key point: Cr and Cu exception)

4. Cu has configuration
   A. [Ar] 3d9 4s2
   B. [Ar] 3d8 4s2
   C. [Ar] 3d10 4s1
   D. [Ar] 3d11
   Answer: C. Full d10 gives stability. (Key point: Cu config)

## Related in Engineering Chemistry

- [General outer electronic configuration of transition elements](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Atm-general-config) — Engineering Chemistry, chapter 5
- [Characteristics of transition series; first-row configuration](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Atm-characteristics-config) — Engineering Chemistry, chapter 5
- [d-block elements; 3d configuration; non-typical metals](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Adblock-config-not-typical) — Engineering Chemistry, chapter 5
- [Transition elements; non-typical 3d element](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Atm-not-typical) — Engineering Chemistry, chapter 5
- [Zn and Cd not typical transition metals](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Azn-cd-not-typical) — Engineering Chemistry, chapter 5
- [Transition elements; configuration; paramagnetism](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Atm-config-paramagnetism) — Engineering Chemistry, chapter 5

## Related in other subjects

- [Elements of transition curve](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Atransition-curve-elements) — Surveying II, chapter 6