Question

Transition metals, when they form interstitial compounds, the non-metals \((\mathrm{H}, \mathrm{B}, \mathrm{C}, \mathrm{N})\) are accomodated in : (a) Voids or holes in cubic-packed structure (b) Tetrahedral voids (c) Octahedral voids (d) All of these

Short answer

The non-metals (H, B, C, N) can be accommodated in all of these: tetrahedral voids, octahedral voids, and other voids in cubic-packed structures.

Step-by-step solution

Understand Interstitial Compounds

Interstitial compounds are formed when small atoms like Hydrogen (H), Boron (B), Carbon (C), and Nitrogen (N) fill the voids or interstices in the crystal lattice of transition metals without disturbing the original metal lattice.

Identify the Types of Voids in Crystal Lattices

In metallic crystals, there are typically two types of voids where interstitial atoms can be accommodated: tetrahedral voids and octahedral voids.

Determine the Correct Answer

Considering the size of non-metals like H, B, C, N, they can be accommodated into the voids of the metal lattices, including both tetrahedral and octahedral voids. For some transition metals that crystallize in cubic-packed structures, additional types of voids may also accommodate non-metals.

Key concepts

Tetrahedral and Octahedral Voids

Understanding the arrangement of atoms in a crystal is key to grasping the concept of interstitial compounds in transition metals. In these compounds, small non-metal atoms like hydrogen (H), boron (B), carbon (C), and nitrogen (N) are inserted into the spaces, or 'voids,' between the larger metal atoms without distorting the crystal structure.

There are two prominent types of voids: tetrahedral voids and octahedral voids. A tetrahedral void is formed by four metal atoms situated at the corners of a tetrahedron. Octahedral voids, on the other hand, involve six metal atoms at the corners of an octahedron. The smaller non-metal atoms fit into these voids, and the type of void they occupy depends on their size relative to the void size. For example, carbon atoms in steel structure are small enough to fit into tetrahedral voids, significantly altering the properties of the metal.

Crystal Lattice Structures

The crystal lattice is a repetitive and highly ordered structure of atoms in a crystalline solid. Each point in the lattice is called a lattice point, and every point is identical in environment to all others. Transition metals often form face-centered cubic (fcc) or body-centered cubic (bcc) lattices.

In an fcc lattice, atoms are located at each corner of the cube and the centers of all the cube faces. This arrangement leaves space for octahedral and tetrahedral voids to exist. In a bcc lattice, atoms sit at the cube corners and a single atom at the center, resulting in a different void distribution. The arrangement impacts not only the density and packing of the crystals but also their chemical and physical properties. Transition metals utilize these lattices to accommodate interstitial atoms, which can modify their characteristics like hardness, ductility, and tensile strength.

Transition Metal Chemistry

Transition metals are elements that have partially filled d or f electron sub-shells in any common oxidation state. They possess unique properties like malleability, high melting and boiling points, and the ability to form various compounds with distinctive colors.

The chemistry of transition metals is complex due to their ability to exhibit multiple oxidation states, form complexes with ligands, and their catalytic behavior. Interstitial compounds are a prime example of transition metal chemistry where non-metal atoms are incorporated into the metal's crystal lattice. This not only strengthens the metal but can also affect its electrical and thermal properties. Understanding these concepts can be crucial for students preparing for competitive exams like the Joint Entrance Examination (JEE) for admissions in engineering colleges in India, where intricacies of chemistry are tested at a deep level.

JEE Chemistry Problems

JEE Chemistry encompasses a wide range of topics, and interstitial compounds are often tested in the Inorganic Chemistry section. When solving JEE problems, it's essential to comprehend the chemical concepts and apply them logically. This includes understanding interstitial compounds, their formation, the types of voids available in crystal lattices, and how these voids are utilized by different sizes of non-metal atoms.

Students are advised to practice problems focusing on the structures of crystal lattices, the positioning of atoms within these lattices, and predicting the properties of the resulting compounds. By mastering these core concepts and relating them to the periodic table's transition metals, students can improve their problem-solving abilities and boost their performance in the exams.