---
title: "Transition elements; why so called; 3d configurations"
subject: "Engineering Chemistry"
chapter: 5
key: "semester_2/engineering_chemistry:tm-called-config"
source: https://www.bctengineer.com/q/semester_2/engineering_chemistry/tm-called-config
site: BCT Engineering
---

# Transition elements; why so called; 3d configurations

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

- Asked in: 2069 Poush, 1+1+3 marks
- Video: [Introduction to d-block elements | The d-block elements | Chemistry | Khan Academy](https://www.youtube.com/watch?v=pgp2sECqClc) — Khan Academy India - English
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_2/engineering_chemistry/tm-called-config
- Whole chapter: https://www.bctengineer.com/md/semester_2/engineering_chemistry/chapter-5

## Question

What are transition elements? Why are they so called? Write down the electronic configurations of 3D series.

## Short answer

Transition elements are d-block elements with partly filled d-subshell in neutral or ionic state. They are so called as they bridge highly electropositive s-block and electronegative p-block, showing transitional properties. Electronic configurations: Sc [Ar]3d¹4s² to Zn [Ar]3d¹⁰4s²; exceptions Cr [Ar]3d⁵4s¹ and Cu [Ar]3d¹⁰4s¹ due to extra stability of half-filled and fully filled d subshells.

## Answer

#### Transition elements
Transition elements are the d-block elements that have a partly filled d-subshell in the atom or in at least one of their common oxidation states. The 3d series is Sc to Zn (general outer configuration (n−1)d¹⁻¹⁰ ns¹⁻²).

#### Why so called
They are placed between the s-block (highly electropositive) and p-block (electronegative) elements, and their properties are transitional between the two. Their atoms or ions have incompletely filled d orbitals.

#### Configurations of the 3d series
```text
Sc  [Ar] 3d¹ 4s²     Fe  [Ar] 3d⁶ 4s²
Ti  [Ar] 3d² 4s²     Co  [Ar] 3d⁷ 4s²
V   [Ar] 3d³ 4s²     Ni  [Ar] 3d⁸ 4s²
Cr  [Ar] 3d⁵ 4s¹     Cu  [Ar] 3d¹⁰ 4s¹
Mn  [Ar] 3d⁵ 4s²     Zn  [Ar] 3d¹⁰ 4s²
```
Cr and Cu are exceptions: a half-filled (d⁵) or completely filled (d¹⁰) 3d subshell is extra stable, so one 4s electron moves into 3d.

## Check yourself

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

1. Transition elements are d-block elements with
   A. a full s subshell only
   B. a partly filled d subshell in the atom or a common oxidation state
   C. no d electrons
   D. a full p subshell
   Answer: B. This is the definition. (Key point: Definition)

2. Why are they so called?
   A. They are artificial
   B. They transit between liquids and solids
   C. They lie between s-block and p-block, with transitional properties
   D. They are in group 18
   Answer: C. Properties are intermediate between the two blocks. (Key point: Why so called)

3. What is Cu?
   A. [Ar] 3d9 4s2
   B. [Ar] 3d8 4s2
   C. [Ar] 3d10 4s2
   D. [Ar] 3d10 4s1
   Answer: D. A 4s electron moves to complete d10. (Key point: Cu configuration)

4. What is Mn?
   A. [Ar] 3d5 4s2
   B. [Ar] 3d6 4s1
   C. [Ar] 3d7 4s0
   D. [Ar] 3d4 4s2
   Answer: A. Mn follows the normal order, with half-filled 3d5. (Key point: Mn configuration)

## Related in Engineering Chemistry

- [Why d-block elements are called transition](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Awhy-transition-elements) — Engineering Chemistry, chapter 5, asked 2×
- [Why 3d elements are transition; valency characteristics](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3A3d-transition-valency) — 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
- [Transition elements; oxidation states of 3d; alloys](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Atm-ox-alloy) — Engineering Chemistry, chapter 5
- [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
- [Main characteristics of 3d transition elements](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3A3d-characteristics) — Engineering Chemistry, chapter 5

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