CSIR NET Chemical Sciences Inorganic Chemistry Syllabus

Why does the stability of carbonates and the solubility of hydroxides change down Group 2?

Down Group 2, thermal stability of carbonates increases (larger cation stabilizes the large carbonate anion) and solubility of hydroxides increases (lattice energy decreases faster than hydration energy), while sulphate solubility decreases.

What is the inert pair effect and where is it most prominent in the p-block?

The inert pair effect is the reluctance of the ns^2 electron pair to participate in bonding in heavier p-block elements, making lower oxidation states more stable down a group (e.g., Tl+ > Tl3+, Pb2+ > Pb4+, Bi3+ > Bi5+).

Compare the acidic/basic nature of p-block element oxides across a period.

Across a period, oxide character changes from basic (metals, e.g., Na2O) through amphoteric (e.g., Al2O3) to acidic (non-metals, e.g., SO3, Cl2O7). Acidity increases with increasing non-metallic character.

Why do noble gases (Group 18) have very high ionization energies and low reactivity?

Noble gases have completely filled valence shells (ns^2 np^6, except He which is 1s^2), giving them very stable electronic configurations, high ionization energies, and positive electron affinities, so they are largely chemically inert.

How does the hydride character change across the p-block, with examples?

p-block hydrides range from acidic (e.g., HCl, H2S) to neutral/weakly basic. Down Group 15 the basicity of hydrides decreases (NH3 > PH3 > AsH3 > SbH3) and thermal stability decreases as bond strength weakens.

What are the general characteristics that define transition (d-block) elements?

Transition elements have partially filled d-orbitals in elemental or common ionic states. They show variable oxidation states, form colored ions and complexes, exhibit catalytic and magnetic properties, and tend to form alloys.

Why do transition metals form complexes readily?

Transition metal ions are small, have high charge density, and possess available low-energy vacant d-orbitals that can accept lone pairs from ligands, enabling strong metal-ligand bonding and stable complex formation.

Why are most transition metal compounds colored?

Color arises from d-d electronic transitions: ligands split the d-orbitals, and electrons absorb visible light to jump from lower to higher d-orbitals. The complementary color of the absorbed wavelength is observed. Ions with d0 or d10 configurations are usually colorless.

Give two examples of transition metals/compounds acting as catalysts and the processes they catalyze.

Iron (Fe) in the Haber process (N2 + H2 -> NH3); Vanadium pentoxide (V2O5) in the Contact process (SO2 -> SO3); Nickel in hydrogenation; Pt/Rh in catalytic converters.

What is the lanthanide contraction and one of its consequences?

The lanthanide contraction is the steady decrease in atomic and ionic radii across the lanthanide series due to poor shielding by 4f electrons. A consequence is that second- and third-row transition elements (e.g., Zr/Hf) have nearly identical radii and similar properties.

What is the most common and most stable oxidation state of lanthanides, and which show +2 or +4?

The characteristic stable oxidation state of lanthanides is +3. Some show +2 (e.g., Eu2+, Yb2+) or +4 (e.g., Ce4+, Tb4+) due to stable empty, half-filled, or filled 4f configurations.

How do actinides differ from lanthanides in oxidation states and reactivity?

Actinides show a wider range of oxidation states (e.g., +3 to +7, with +4, +5, +6 common in early actinides) because 5f, 6d, and 7s energies are close. They are more reactive, and many are radioactive.

Name the principal method used to separate individual lanthanides and the basis of separation.

Ion-exchange chromatography (and solvent extraction) is the principal modern method. Separation is based on the slight differences in ionic size/charge density (from the lanthanide contraction), which affect the stability of complexes formed with eluting/complexing agents like citrate or EDTA.

State the IUPAC rule for the order of naming ligands and the metal in a coordination compound.

In the formula, the metal is written first then ligands; in the name, ligands are named first in alphabetical order, then the metal. Anionic complexes take the suffix -ate. The metal oxidation state is given in Roman numerals in parentheses.

How are anionic, neutral, and cationic ligands named (with examples)?

Anionic ligands end in -o (e.g., Cl- = chlorido, CN- = cyanido, OH- = hydroxido, SO4^2- = sulfato). Neutral ligands keep their name with key exceptions: H2O = aqua, NH3 = ammine, CO = carbonyl, NO = nitrosyl.

Distinguish geometrical (cis-trans) isomerism from optical isomerism in coordination compounds.

Geometrical isomerism arises from different spatial arrangements of ligands (cis = adjacent, trans = opposite), common in square planar MA2B2 and octahedral complexes. Optical isomerism arises when a complex is non-superimposable on its mirror image (chiral), e.g., [Co(en)3]^3+.

Name four types of structural isomerism in coordination compounds.

Ionization isomerism, hydrate (solvate) isomerism, linkage isomerism (ambidentate ligands like NO2-/ONO-), and coordination isomerism.

How does Valence Bond Theory explain bonding and geometry in [Ni(CN)4]^2- vs [NiCl4]^2-?

[Ni(CN)4]^2- uses dsp2 hybridization (strong-field CN- causes pairing), giving square planar, diamagnetic. [NiCl4]^2- uses sp3 hybridization (weak-field Cl-), giving tetrahedral, paramagnetic with 2 unpaired electrons.

State the 18-electron rule and its significance for organometallic complexes.

The 18-electron rule states that stable transition-metal organometallic complexes tend to have 18 valence electrons (filling s, p, and d orbitals), analogous to the noble gas configuration. It predicts stability and electron count in carbonyls and other complexes.

Give two important applications of coordination compounds.

Examples: EDTA complexation in water-hardness estimation and metal-ion sequestration; cisplatin [Pt(NH3)2Cl2] as an anticancer drug; chlorophyll (Mg) and hemoglobin (Fe) in biology; electroplating using cyanide complexes; metallurgical extraction (e.g., gold via cyanide complex).

What is the chelate effect?

The chelate effect is the enhanced stability of complexes containing chelating (polydentate) ligands compared with those containing equivalent numbers of monodentate ligands, driven largely by a favorable (positive) entropy change upon chelation.

Name a key step in homogeneous catalysis cycles such as hydroformylation or Wacker process.

Common elementary steps include oxidative addition, migratory insertion (of CO or alkene), ligand substitution, and reductive elimination. Hydroformylation (oxo process) uses Co or Rh catalysts to convert alkene + CO + H2 to aldehydes.

Name two important metalloproteins/metalloenzymes and the metal and function of each.

Hemoglobin/myoglobin (Fe, O2 transport/storage); cytochromes (Fe, electron transfer); carbonic anhydrase (Zn, CO2 hydration); carboxypeptidase (Zn, peptide hydrolysis); nitrogenase (Fe-Mo, N2 fixation); chlorophyll (Mg, photosynthesis).

What are the roles of Na+/K+ and Ca2+ ions in biological systems?

Na+/K+ maintain osmotic balance, membrane potentials, and nerve impulse transmission (via the Na+/K+ ATPase pump). Ca2+ functions in bone/teeth structure, muscle contraction, blood clotting, and as an intracellular signaling messenger.

What electronic transitions are probed by UV-Visible spectroscopy and what is the Beer-Lambert law?

UV-Vis probes electronic transitions (sigma->sigma*, n->sigma*, n->pi*, pi->pi*, and d-d/charge-transfer). Beer-Lambert law: A = epsilon * c * l, where A is absorbance, epsilon molar absorptivity, c concentration, and l path length.

What molecular property does IR spectroscopy measure, and what is the IR-active selection rule?

IR spectroscopy measures molecular vibrations (stretching and bending). A vibration is IR-active only if it produces a change in the molecule's dipole moment. Characteristic regions: O-H/N-H ~3200-3600, C=O ~1700 cm^-1.

In NMR spectroscopy, what do chemical shift, integration, and spin-spin splitting (n+1 rule) tell you?

Chemical shift indicates the electronic environment of a nucleus; integration gives the relative number of equivalent nuclei; spin-spin splitting follows the n+1 rule, where n equivalent neighboring nuclei split a signal into n+1 peaks, revealing connectivity.

What information does mass spectrometry provide, and what are the molecular ion and base peak?

Mass spectrometry gives molecular mass and structural fragments via mass-to-charge (m/z) ratios. The molecular ion (M+) corresponds to the intact molecule's mass; the base peak is the most intense peak (assigned 100% relative abundance).

What is the principle of volumetric (titrimetric) analysis and the equivalence-point relation?

Volumetric analysis determines an analyte's concentration by reacting it with a standard solution of known concentration until the equivalence point, detected by an indicator. Relation: N1V1 = N2V2 (or moles reacting in stoichiometric ratio).

What is gravimetric analysis and what is a key requirement of the precipitate formed?

Gravimetric analysis determines the amount of an analyte by converting it to a pure, insoluble precipitate of known composition, which is filtered, dried/ignited, and weighed. The precipitate must be of low solubility, high purity, and a definite, weighable chemical form.

What is the basic principle of chromatographic separation, and name three types?

Chromatography separates components based on their differential distribution between a stationary phase and a mobile phase. Types: paper chromatography, thin-layer chromatography (TLC), column chromatography, gas chromatography (GC), and high-performance liquid chromatography (HPLC). Rf = distance traveled by solute / distance traveled by solvent front.