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Position of d-Block Elements in the Periodic Table

d-block elements are elements in which the differentiating electron enters the d-subshell of the penultimate shell. They are placed between the s-block and p-block elements in the periodic table.

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Student-friendly explanation

The d-block occupies groups 3 to 12. The first transition series is the 3d series from scandium to zinc. Transition elements are generally defined as elements that have partially filled d-orbitals in their atoms or common ions, so zinc, cadmium, and mercury are often treated carefully because their common +2 ions have completely filled d10 configurations.

How to write this in exams

  1. 1

    Start with the exact idea

    d-block elements are elements in which the differentiating electron enters the d-subshell of the penultimate shell. They are placed between the s-block and p-block elements in the periodic table.

  2. 2

    Then show how to use it

    Write the electronic configuration, remove ns electrons before (n-1)d electrons when forming cations, then check whether the resulting common ion has an incomplete d-subshell.

  3. 3

    Add one concrete example

    In the first transition series, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn are 3d-block elements. Fe is a typical transition element because Fe2+ and Fe3+ contain partially filled d-orbitals.

  4. 4

    Avoid this incomplete answer

    A common wrong answer is saying Zn is a typical transition element only because it is in the d-block, ignoring the d10 configuration of Zn2+.

Definition

d-block elements are elements in which the differentiating electron enters the d-subshell of the penultimate shell. They are placed between the s-block and p-block elements in the periodic table.

Example

In the first transition series, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn are 3d-block elements. Fe is a typical transition element because Fe2+ and Fe3+ contain partially filled d-orbitals.

Rule to remember

Rule: d-block elements have differentiating electrons entering (n-1)d orbitals. Transition-element check: atom or common ion should have an incomplete d-subshell.

Memory hook

d-block is a place; transition behaviour needs incomplete d-orbitals.

Examples and method

Worked example

Identify whether Cu is a transition element. Cu has configuration [Ar] 3d10 4s1, and Cu2+ has 3d9 configuration. Since Cu2+ has an incomplete d-subshell, copper is considered a transition element.

Method to apply

Write the electronic configuration, remove ns electrons before (n-1)d electrons when forming cations, then check whether the resulting common ion has an incomplete d-subshell.

Diagram support

A periodic-table block diagram can help students locate groups 3 to 12 between s-block and p-block, but a full diagram is not essential for answering most exam questions.

How CBSE asks it

Questions usually ask students to define transition elements, locate the 3d series, or explain why Zn, Cd, and Hg are not typical transition elements.

Avoid common mistakes

Common confusion

Students often call every d-block element a transition element without checking whether the atom or its common ion has a partially filled d-subshell. Zn is d-block, but Zn2+ is d10 and does not show many typical transition properties.

Common wrong answer

A common wrong answer is saying Zn is a typical transition element only because it is in the d-block, ignoring the d10 configuration of Zn2+.

Exam tip

For classification questions, first identify the block by the subshell receiving the differentiating electron, then decide whether it is a transition element by checking partial d-orbital occupancy in the atom or common ion.

Quick check

Why is iron considered a transition element while zinc is usually not considered a typical transition element?

Iron forms ions such as Fe2+ and Fe3+ with partially filled d-orbitals, while Zn2+ has a completely filled 3d10 configuration, so zinc lacks many typical transition properties.

Answer writing and exam use

1-mark answer

d-block elements are elements in which the differentiating electron enters the d-subshell of the penultimate shell. They are placed between the s-block and p-block elements in the periodic table.

2-mark answer

d-block elements are elements in which the differentiating electron enters the d-subshell of the penultimate shell. They are placed between the s-block and p-block elements in the periodic table. Rule: d-block elements have differentiating electrons entering (n-1)d orbitals. Transition-element check: atom or common ion should have an incomplete d-subshell. In the first transition series, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn are 3d-block elements. Fe is a typical transition element because Fe2+ and Fe3+ contain partially filled d-orbitals.

3-mark answer

The d-block occupies groups 3 to 12. The first transition series is the 3d series from scandium to zinc. Transition elements are generally defined as elements that have partially filled d-orbitals in their atoms or common ions, so zinc, cadmium, and mercury are often treated carefully because their common +2 ions have completely filled d10 configurations. Rule: d-block elements have differentiating electrons entering (n-1)d orbitals. Transition-element check: atom or common ion should have an incomplete d-subshell. Identify whether Cu is a transition element. Cu has configuration [Ar] 3d10 4s1, and Cu2+ has 3d9 configuration. Since Cu2+ has an incomplete d-subshell, copper is considered a transition element. Questions usually ask students to define transition elements, locate the 3d series, or explain why Zn, Cd, and Hg are not typical transition elements. A common wrong answer is saying Zn is a typical transition element only because it is in the d-block, ignoring the d10 configuration of Zn2+.
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