Most Important Transition Elements MCQs with Answers

As electrons are added to the inner (n-1)d orbitals across a transition series, the increased nuclear charge is partially compensated by the shielding effect of these d-electrons, leading to only a small decrease in atomic radii.

Paramagnetism in transition metal ions is caused by the presence of unpaired electrons in their d-orbitals. Each unpaired electron acts as a tiny magnet.

Transition elements are good conductors of electricity and heat due to the presence of mobile, delocalized valence electrons (both s and d electrons) in their metallic lattice.

Mn²⁺ ([Ar] 3d⁵) is particularly stable due to its half-filled d-subshell configuration, making +2 a very common and stable oxidation state for manganese.

Transition metals form interstitial compounds because their crystal lattices have small vacant spaces (interstitial sites) where small non-metal atoms (like H, B, C, N) can fit.

The color of transition metal ions in solution is due to the absorption of specific wavelengths of visible light, causing electrons to jump from lower to higher energy d-orbitals (d-d transitions). The complementary color is then observed.

Transition elements are true metals and exhibit characteristic metallic properties such as high tensile strength, ductility, malleability, and metallic luster.

The spin-only magnetic moment (μ) of a transition metal ion is calculated using the formula μ = √n(n+2) BM, where 'n' is the number of unpaired electrons.

Transition metals generally have high densities due to their relatively small atomic volumes (compact crystal structures) and high atomic masses.

The +2 oxidation state is common for most transition elements, resulting from the loss of the two outermost s-electrons. This is often the first stable oxidation state observed.

Ligands are ions or neutral molecules that bind to the central metal atom or ion in a complex compound, forming a coordinate bond.

The coordination number is defined as the number of ligand atoms or ions directly bonded to the central metal ion in a complex.

Ethylenediamine (en) is a bidentate ligand because it can form two coordinate bonds with the central metal atom through its two nitrogen atoms. Chloride, water, and ammonia are monodentate.

In [Co(NH₃)₆]Cl₃, there are six ammonia (NH₃) ligands directly attached to the central cobalt (Co) ion. Thus, the coordination number is 6.

The ligands are named first, followed by the metal. "di" indicates two ammonia ligands (ammine). The oxidation state of silver is +1, indicated by (I).

In hexacyanoferrate(II), the iron is in the +2 oxidation state. With six cyanide ligands (each -1 charge), the complex ion [Fe(CN)₆] has a charge of -4. To balance this, four potassium ions (each +1) are needed, hence K₄[Fe(CN)₆].

Complexes with a coordination number of 4 commonly adopt either a tetrahedral geometry (e.g., [NiCl₄]²⁻) or a square planar geometry (e.g., [Pt(NH₃)₂Cl₂]).

The coordination sphere includes the central metal atom or ion and the ligands directly bonded to it, enclosed in a square bracket in the formula, indicating they are part of the complex ion.

In complex compounds, ligands donate electron pairs to the central metal ion to form coordinate covalent or dative bonds.

Water (H₂O) acts as a neutral ligand (aqua) in complex compounds, donating an electron pair from the oxygen atom. Cyanide, chloride, and sulfate are anionic ligands.

Carbonyl (CO) is a neutral ligand. Since there are no other charged species, the oxidation state of Nickel must be 0 to maintain overall neutrality of the complex.

Square planar geometry is characteristic of many complexes involving d⁸ central metal ions, especially those of 2nd and 3rd row transition elements (like Pt²⁺, Pd²⁺, Au³⁺).

Ligands are named alphabetically: 'aqua' (water) comes before 'chloro'. The prefix 'tetra' indicates four waters, 'di' for two chlorides. The oxidation state of Cr is +3. The counter ion is chloride.

A coordination number of 2 typically results in a linear geometry, as seen in complexes like [Ag(NH₃)₂]⁺.

Potassium (K) has a +1 charge. Since there are three K⁺ ions, the complex ion [Fe(C₂O₄)₃] must have a charge of -3 to balance the compound's overall neutrality.

A monodentate ligand forms only one coordinate bond with the central metal atom, meaning it has only one donor atom.

Wrought iron is the purest commercial form of iron and contains the lowest percentage of carbon (0.12% to 0.25%).

Pig iron is the crude product obtained from the blast furnace and contains a high percentage of carbon (2.5% to 4.5%) along with other impurities.

Steel contains a higher percentage of carbon (0.25% to 2.5%) compared to wrought iron (0.12% to 0.25%).

The Bessemer's process is one of the earliest methods for the large-scale production of steel from pig iron by blowing air through molten pig iron to oxidize impurities.

Steel is classified into mild, medium carbon, and high carbon steel based on its carbon percentage. "Pure steel" is not a standard classification; steel always contains some carbon.

The puddling furnace is used to convert pig iron into wrought iron by oxidizing and removing impurities like carbon, silicon, and phosphorus.

High carbon steel (0.5% to 1.5% carbon) is very hard and strong, but also more brittle compared to lower carbon steels.

The Open Hearth process is a slower but more controllable process than the Bessemer's process, and it can effectively utilize a significant amount of scrap iron in the steel production.

Cast iron (which is essentially pig iron when solidified and shaped) has a lower melting point and good fluidity, making it suitable for casting into various shapes.

Mild steel typically has a carbon content ranging from 0.05% to 0.25%, making it relatively soft and ductile.

Corrosion is an electrochemical process that involves the oxidation of a metal due to its reaction with the environment, often forming oxides or other salts.

Rusting of iron, a common form of corrosion, requires both oxygen and water to occur. It's an electrochemical process where iron acts as the anode.

In the rusting of iron, iron itself undergoes oxidation (loss of electrons) at the anode, where it forms Fe²⁺ ions.

Galvanizing is the process of coating iron or steel with a thin layer of zinc. Zinc acts as a sacrificial anode, providing cathodic protection to iron.

When the tin coating is scratched or damaged, iron is exposed. Since tin is less reactive than iron, iron acts as the anode and corrodes rapidly in the presence of oxygen and water, sacrificing itself to protect the tin.

Sacrificial protection (a type of cathodic protection) involves connecting a more reactive metal (which acts as a sacrificial anode) to the metal to be protected, making the protected metal the cathode and preventing its oxidation.

The presence of electrolytes (like salts, acids, or bases) in water increases its electrical conductivity, which facilitates the flow of electrons in the electrochemical corrosion process, thus accelerating rusting.

Aluminum forms a thin, tough, non-porous, and adherent layer of aluminum oxide (Al₂O₃) on its surface when exposed to air. This oxide layer prevents further corrosion, a phenomenon known as passivation.