---
title: "Characteristics of transition series; first-row configuration"
subject: "Engineering Chemistry"
chapter: 5
key: "semester_2/engineering_chemistry:tm-characteristics-config"
source: https://www.bctengineer.com/q/semester_2/engineering_chemistry/tm-characteristics-config
site: BCT Engineering
---

# Characteristics of transition series; first-row configuration

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

- Asked in: 2069 Poush, 2+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/tm-characteristics-config
- Whole chapter: https://www.bctengineer.com/md/semester_2/engineering_chemistry/chapter-5

## Question

Give the important characteristics of transition series. Explain the electronic configuration of first transition elements.

## Short answer

Characteristics: hard and dense, high melting points, variable oxidation states, colored ions, paramagnetism, form complexes and alloys, catalytic activity. Electronic configuration: electrons fill 3d after 4s, general [Ar]3d¹⁻¹⁰4s¹⁻²; exceptions Cr [Ar]3d⁵4s¹ and Cu [Ar]3d¹⁰4s¹ due to stable half-filled and full d subshells.

## Answer

#### Important characteristics
1. Hard, dense metals with high melting and boiling points and good electrical conductivity.
2. Variable oxidation states (Mn: +2 to +7).
3. Form coloured ions because of d–d transitions.
4. Paramagnetic due to unpaired d electrons.
5. Form many stable complexes (e.g. [Fe(CN)₆]⁴⁻).
6. Act as catalysts (Fe, Ni, V₂O₅).
7. Form alloys and interstitial compounds.

#### Electronic configuration of the first transition series
Electrons are added to 3d after 4s is filled. Configurations are [Ar] 3d¹⁻¹⁰ 4s¹⁻²:
```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. Which describes transition metals?
   A. Soft, low melting points
   B. Hard, dense, high melting point, good conductors
   C. Poor conductors
   D. Gaseous at room temperature
   Answer: B. These are typical physical characteristics. (Key point: Physical properties)

2. In the first transition series, electrons are added to 3d after
   A. 4p is filled
   B. 3p is emptied
   C. 4s is filled
   D. 5s is filled
   Answer: C. 4s fills before 3d. (Key point: Order of filling)

3. Which two have 4s1?
   A. Fe and Co
   B. Sc and Ti
   C. Mn and Zn
   D. Cr and Cu
   Answer: D. Half-filled/filled 3d is extra stable. (Key point: Exceptions)

4. Which are catalysts?
   A. Fe, Ni and V2O5
   B. Na and K
   C. Cl2 and F2
   D. He and Ne
   Answer: A. Transition metals and compounds catalyse reactions. (Key point: Catalysts)

## Related in Engineering Chemistry

- [Transition elements; first series configuration](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Awhy-transition-elements-typical) — 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
- [First-row configuration; variable oxidation states](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Aconfig-variable-oxidation) — 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
- [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
- [Main characteristics of 3d transition elements](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3A3d-characteristics) — Engineering Chemistry, chapter 5