GATE Life Sciences s, p and d Block Elements Syllabus

s, p and d Block Elements syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for s, p and d Block Elements in GATE Life Sciences, not a summary of it.

1. 1

   Oxides, halides and hydrides of alkali, alkaline earth metals, B, Al, Si, N, P, and S

   2 topics

   • General characteristics of 3d elements
   • Coordination complexes
     • Valence bond theory
     • Crystal field theory
     • Color
     • Geometry
     • Magnetic properties
     • Isomerism

s, p and d Block Elements flashcards for GATE Life Sciences

18 of 50 cards from the s, p and d Block Elements deck — real questions with worked answers.

1. What is the general electronic configuration of the 3d (first transition series) elements?

   $[\text{Ar}]\,3d^{1\text{–}10}\,4s^{1\text{–}2}$. The $3d$ orbitals are progressively filled across the series from Sc to Zn.

2. Why are Zn, Cd and Hg generally not regarded as true transition elements?

   A transition element must have a partially filled $d$ subshell in its ground state or in a common oxidation state. Zn, Cd, Hg have a completely filled $d^{10}$ configuration in both the atom and their common $+2$ ions, so they do not show typical transition-metal behaviour.

3. Which two 3d elements have anomalous electronic configurations, and what are they?

   Chromium: $[\text{Ar}]\,3d^{5}\,4s^{1}$ and Copper: $[\text{Ar}]\,3d^{10}\,4s^{1}$. These arise from the extra stability of exactly half-filled ($d^{5}$) and fully-filled ($d^{10}$) subshells.

4. Why do transition metals commonly exhibit variable oxidation states?

   Because the energies of the $3d$ and $4s$ orbitals are very close, electrons from both subshells can participate in bonding. This allows successive removal of electrons with comparable ionization energies, giving multiple oxidation states (often differing by one unit).

5. What is the maximum oxidation state shown by manganese, and in which compound is it seen?

   $+7$, as in the permanganate ion $\ce{MnO4^-}$ (e.g. $\ce{KMnO4}$). It corresponds to the use of all $3d^{5}4s^{2}$ electrons.

6. Why do transition metals have high melting and boiling points compared to s-block metals?

   They have a large number of unpaired $d$-electrons that participate in metallic bonding, giving strong interatomic (and covalent-like $d$–$d$) bonding. Strength peaks around the middle of the series where unpaired electrons are maximal.

7. Why do most transition metal compounds and ions appear coloured?

   Colour arises from $d$–$d$ electronic transitions: an electron in a lower-energy $d$ orbital absorbs a photon of energy equal to the crystal-field splitting $\Delta$ and is promoted to a higher-energy $d$ orbital. The complementary colour to the absorbed wavelength is observed.

8. Why are $\ce{Zn^2+}$, $\ce{Cu+}$ and $\ce{Sc^3+}$ ions colourless?

   They have either completely filled ($d^{10}$ for $\ce{Zn^2+}$, $\ce{Cu+}$) or completely empty ($d^{0}$ for $\ce{Sc^3+}$) $d$ subshells, so no $d$–$d$ transitions are possible.

9. Define a coordination compound (complex).

   A compound containing a central metal atom or ion bonded to a fixed number of surrounding ions or molecules (ligands) by coordinate (dative) bonds, which retains its identity even in solution. Example: $\ce{[Cu(NH3)4]^2+}$.

10. What is a ligand, and what must a ligand possess?

    A ligand is an ion or molecule bonded to the central metal atom/ion through a coordinate bond. It must possess at least one lone pair of electrons (or $\pi$ electrons) to donate to the metal, i.e. it acts as a Lewis base.

11. Define the coordination number of a central metal ion in a complex.

    The number of ligand donor atoms directly bonded (coordinated) to the central metal ion through sigma coordinate bonds. For example, in $\ce{[Fe(CN)6]^4-}$ the coordination number is $6$.

12. Distinguish between monodentate, bidentate and polydentate (chelating) ligands with examples.

    Monodentate: donates through one atom (e.g. $\ce{NH3}$, $\ce{Cl-}$). Bidentate: donates through two atoms (e.g. ethylenediamine 'en', oxalate $\ce{C2O4^2-}$). Polydentate: donates through many atoms (e.g. EDTA$^{4-}$, hexadentate).

13. What is a chelate, and why are chelate complexes especially stable?

    A chelate is a ring structure formed when a polydentate ligand binds a metal through two or more donor atoms. Their extra stability (the chelate effect) is largely entropy-driven: ring formation releases more free ligand molecules, increasing the number of particles and hence $\Delta S$.

14. State the denticity and donor atoms of EDTA$^{4-}$.

    EDTA$^{4-}$ is hexadentate (denticity $= 6$): it donates through $2$ nitrogen atoms and $4$ oxygen atoms (from carboxylate groups), wrapping around the metal to form a very stable octahedral complex.

15. What is an ambidentate ligand? Give two examples.

    A monodentate ligand that can coordinate through either of two different donor atoms. Examples: nitrite $\ce{NO2^-}$ (binds via N as nitro or via O as nitrito) and thiocyanate $\ce{SCN^-}$ (binds via S as thiocyanato or via N as isothiocyanato).

16. What is the central postulate of Valence Bond Theory (VBT) for coordination complexes?

    The central metal ion provides a number of empty hybrid orbitals (formed by hybridization of $s$, $p$ and $d$ orbitals) equal to its coordination number; each ligand donates a lone pair into these orbitals, forming coordinate covalent bonds. The geometry is determined by the type of hybridization.

17. According to VBT, what hybridization and geometry correspond to coordination numbers 4 (two types) and 6?

    CN $4$ tetrahedral: $sp^{3}$; CN $4$ square planar: $dsp^{2}$. CN $6$ octahedral: $d^{2}sp^{3}$ (inner orbital, uses $3d$) or $sp^{3}d^{2}$ (outer orbital, uses $4d$).

18. In VBT, distinguish inner-orbital (low-spin) and outer-orbital (high-spin) octahedral complexes.

    Inner-orbital complexes use inner $(n-1)d$ orbitals giving $d^{2}sp^{3}$ hybridization (formed with strong-field ligands, usually low-spin). Outer-orbital complexes use outer $nd$ orbitals giving $sp^{3}d^{2}$ hybridization (formed with weak-field ligands, high-spin).

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