Question

The element having the electronic configuration \([\mathrm{Kr}] 4 \mathrm{~d}^{10} 4 \mathrm{f}^{14} 5 \mathrm{~s}^{2} 5 \mathrm{p}^{6} 5 \mathrm{~d}^{2} 6 \mathrm{~s}^{2}\) belongs to (a) s-block (b) p-block (c) d-block (d) f-block

Short answer

Answer: c) d-block

Step-by-step solution

Identify highest energy subshell with electrons

In the given electronic configuration \([\mathrm{Kr}] 4\mathrm{~d}^{10} 4 \mathrm{f}^{14} 5 \mathrm{~s}^{2} 5 \mathrm{p}^{6} 5\mathrm{~d}^{2} 6 \mathrm{~s}^{2}\), the subshells are filled in order of energy. The highest energy subshell with electrons is 5d, which contains 2 electrons.

Determine which block of the periodic table the element belongs to

Since the highest energy subshell with electrons is the 5d subshell, the element belongs to the d-block. So, the correct answer is: (c) d-block

Key concepts

Periodic Table Blocks

Understanding the periodic table blocks is fundamental for grasping how elements are organized based on their electronic configurations. The periodic table is divided into four distinct blocks: the s-block, p-block, d-block, and f-block. Each block is named after the orbital type that is being filled with electrons in the elements within that block.

For example, the s-block contains elements where the s orbital is being filled. This includes all group 1 (alkali metals) and group 2 (alkaline earth metals) elements, plus helium. The p-block contains groups 13 to 18, which include elements from boron to the noble gases that are filling their p orbitals. Similarly, transition metals which fill d orbitals belong to the d-block, and the actinides and lanthanides filling f orbitals make up the f-block.

Understanding these blocks helps students to quickly determine the properties of elements, their possible reactions, and their location on the periodic table. When identifying an element's block, one simply needs to look at the highest energy level of electrons and match it to the corresponding block.

D-block Elements

The d-block elements, also known as transition metals, are found in the central region of the periodic table. These elements are characterized by the progressive filling of the d orbitals with electrons, starting from scandium (Sc) to zinc (Zn) in the first row, and similar patterns in the subsequent rows.

D-block elements are unique as they often exhibit variable oxidation states and form colored compounds. They are often involved in catalysis and are crucial for numerous industrial processes. The distinguishing feature of a d-block element is that its d orbitals are filled with electrons after the s orbitals of that particular energy level have already been filled. However, the elements are classified into the d-block based on the highest energy d subshell that is being filled with electrons, rather than the number of d electrons that an element has.

Electron Subshell Filling

Electron subshells fill according to a specific order which follows the principles encapsulated by the Aufbau principle, Hund's rule, and the Pauli exclusion principle. The Aufbau principle explains that electrons fill orbitals starting from those with the lowest energy first. The sequence in which subshells get filled is based on their increasing energy levels, typically following this sequence: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, and so on.

This filling pattern generally guides us to predict the electron configuration of an element, but there are exceptions due to electron-electron interactions and overall energy minimization. Subshells across different energy levels can overlap in their energy; for example, the 4s subshell is filled before the 3d, despite being a higher principal quantum number. This nuanced filling order is vital in understanding electronic configurations and predicting chemical behaviors of elements.