Question

Non-stoichiometric hydrides are produced by (a) palladium, vanadium (b) manganese, lithium (c) nitrogen, fuorine (d) carbon, nickel

Short answer

Non-stoichiometric hydrides are produced by palladium and vanadium because they are transition metals capable of forming hydrides with a non-fixed hydrogen-to-metal ratio.

Step-by-step solution

Understanding Non-stoichiometric Hydrides

Non-stoichiometric hydrides are formed by elements that can host hydrogen atoms in interstitial sites within their crystal lattice, leading to a hydrogen-to-metal ratio that is not fixed. Typically, these are transition metals, which can accommodate more hydrogen atoms due to their metal lattice.

Assessing Options for Non-stoichiometric Hydride Formation

Upon reviewing the given options, we must look for transition metals known to form hydrides of variable compositions. Palladium and vanadium are both transition metals that can absorb hydrogen atoms in their lattice to form non-stoichiometric hydrides.

Eliminating Incorrect Options

Manganese and lithium form stoichiometric hydrides, meaning they have specific hydrogen-to-metal ratios. Nitrogen and fluorine are nonmetals and do not form hydrides in this manner. Carbon does not typically form metal hydrides, and nickel forms mostly stoichiometric hydrides. Therefore, these are not the correct options.

Identifying the Correct Answer

Based on the understanding of non-stoichiometric hydrides and the given options, palladium and vanadium are the correct choices for elements that produce non-stoichiometric hydrides.

Key concepts

Transition Metals in Chemistry

Transition metals are elements found in the middle of the periodic table, specifically in groups 3 through 12. They are known for their ability to form positively charged ions with various oxidation states. This feature is a result of the filling of their d electron shells, which influences their chemical reactivity and bonding characteristics.

When it comes to their role in hydride formation, transition metals like palladium and vanadium standout due to their unique electronic configurations. These metals have empty d or f orbitals that can participate in bonding, allowing them to absorb hydrogen atoms and form non-stoichiometric hydrides. The flexibility in their oxidation states enables them to accommodate varying amounts of hydrogen, which is why they often deviate from strict stoichiometry. Furthermore, the catalytic properties of transition metals are critical in various industrial processes, including hydrogenation reactions.

• Transition metals have variable oxidation states.
• They form colored compounds.
• Palladium and vanadium are transition metals known for absorbing hydrogen.

Hydrogen Absorption in Metals

Hydrogen absorption in metals is a fascinating phenomenon that has significant industrial and technological implications, such as in fuel cells and hydrogen storage materials. Metals that absorb hydrogen will generally incorporate hydrogen atoms into their crystal lattice, either in interstitial sites or by forming metallic bonds with the hydrogen.

In the specific case of non-stoichiometric hydrides, the metal absorbs hydrogen without a fixed ratio between the metal and hydrogen atoms, often resulting in a range of compositions. Transition metals are particularly adept at this due to their loosely filled d orbitals, which allow for more flexible bonding arrangements and the ability to host additional hydrogen atoms without altering their overall structure significantly.The process of hydrogen absorption can therefore fundamentally alter the electrical and mechanical properties of the metal, which requires careful consideration when these materials are utilized in real-world applications.

Key points to remember include:

• Metals can absorb hydrogen into their crystal lattice.
• Transition metals are especially good at absorbing hydrogen due to their electronic structure.
• Non-stoichiometric hydrides do not have a fixed hydrogen-to-metal ratio.

Crystal Lattice Structure

The crystal lattice structure of a metal is a highly ordered arrangement of atoms in a three-dimensional grid. This structure is fundamental in defining many of the characteristics of metals, including their strength, malleability, electrical and thermal conductivity, and ability to form alloys.

When discussing hydrides, especially non-stoichiometric hydrides, we are concerned with how hydrogen atoms integrate into this crystal lattice. Hydrogen atoms can occupy interstitial sites, which are the spaces between the metal atoms. Due to the small size of hydrogen, it can fit into these interstices without substantially disrupting the lattice. Such absorption leads to the formation of a metal hydride, which can exhibit unique properties different from the parent metal.

Understanding how hydrogen atoms interact with and are accommodated by the crystal lattice is key when studying non-stoichiometric hydrides. The varying amounts of hydrogen can disturb the lattice to different degrees, resulting in a diverse range of material properties that are promising for various technologies.A few quick facts about crystal lattices are:

• They define the structure and many properties of metals.
• Hydrogen atoms can be incorporated into the lattice at interstitial sites.
• The insertion of hydrogen can alter the metal's properties.