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d-and f-Block Elements - Position in the Periodic Table

Grade 12CBSEChemistry

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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The dd-block elements are found in Groups 3 to 12 of the periodic table, occupying the central part between the ss-block and pp-block elements.

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A transition element is defined as one which has incompletely filled dd-orbitals in its ground state or in any one of its common oxidation states.

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The dd-block consists of four series: 3d3d series (ScSc to ZnZn), 4d4d series (YY to CdCd), 5d5d series (LaLa, HfHf to HgHg), and 6d6d series (which is incomplete).

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Zn,Cd,Zn, Cd, and HgHg of group 12 have full d10d^{10} configuration in their ground state as well as in their common oxidation states and are therefore not regarded as transition metals.

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The ff-block elements, also known as inner transition elements, consist of two series: Lanthanoids (filling of 4f4f orbitals) and Actinoids (filling of 5f5f orbitals), placed separately at the bottom of the periodic table.

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The transition elements are so named because their properties represent a transition between the highly electropositive ss-block elements and the highly electronegative pp-block elements.

📐Formulae

General electronic configuration of d-block elements: (n−1)d1−10ns1−2\text{General electronic configuration of } d\text{-block elements: } (n-1)d^{1-10} ns^{1-2}

General electronic configuration of f-block elements: (n−2)f1−14(n−1)d0−1ns2\text{General electronic configuration of } f\text{-block elements: } (n-2)f^{1-14} (n-1)d^{0-1} ns^2

Electronic configuration of Chromium (Cr, Z=24): [Ar]3d54s1\text{Electronic configuration of Chromium (Cr, Z=24): } [Ar] 3d^5 4s^1

Electronic configuration of Copper (Cu, Z=29): [Ar]3d104s1\text{Electronic configuration of Copper (Cu, Z=29): } [Ar] 3d^{10} 4s^1

💡Examples

Problem 1:

On what basis can you say that Scandium (Z=21Z = 21) is a transition element but Zinc (Z=30Z = 30) is not?

Solution:

Scandium (Z=21Z = 21) has the ground state electronic configuration [Ar]3d14s2[Ar] 3d^1 4s^2. Since it has an incompletely filled 3d3d orbital, it is a transition element. Zinc (Z=30Z = 30) has the configuration [Ar]3d104s2[Ar] 3d^{10} 4s^2 in its ground state and [Ar]3d10[Ar] 3d^{10} in its +2+2 oxidation state. Since the dd-orbitals are completely filled in both cases, it is not a transition element.

Explanation:

The definition of a transition element requires an incomplete dd-subshell in either the atomic or a common ionic state.

Problem 2:

Silver atom has completely filled dd orbitals (4d104d^{10}) in its ground state. How can you say it is a transition element?

Solution:

Silver (Z=47Z = 47) has the ground state configuration [Kr]4d105s1[Kr] 4d^{10} 5s^1. However, in its common oxidation state +2+2 (Ag2+Ag^{2+}), the configuration becomes [Kr]4d9[Kr] 4d^9.

Explanation:

Because the dd-orbital is incompletely filled in the +2+2 oxidation state, Silver satisfies the definition of a transition element.

Problem 3:

Write the general electronic configuration of Lanthanoids.

Solution:

[Xe]4f1−145d0−16s2[Xe] 4f^{1-14} 5d^{0-1} 6s^2

Explanation:

Lanthanoids involve the filling of the 4f4f subshell. The 5d5d orbital may contain 00 or 11 electron depending on the stability provided by exchange energy (e.g., Gadolinium).