The hybridization of central atom in SO₃ is
A sp
B sp²
C sp³
D sp³d
Sulfur in SO₃ has three σ bonds and no lone pair on the central atom → trigonal planar geometry → sp² hybridization.
Which molecule has zero lone pair on central atom
A NH₃
B H₂O
C BF₃
D SO₂
Boron in BF₃ forms three σ bonds and has no lone pair.
Which molecule shows maximum deviation from ideal bond angle
A CH₄
B NH₃
C H₂O
D CO₂
H₂O has two lone pairs, causing strong LP–LP and LP–BP repulsions, reducing bond angle to ~104.5°.
Which molecule has trigonal planar electron geometry but bent shape
A BF₃
B CO₂
C SO₂
D BeCl₂
SO₂ has three electron domains (two bonds + one lone pair). Electron geometry is trigonal planar, but shape is bent.
The bond angle order is
A CH₄ > NH₃ > H₂O
B NH₃ > CH₄ > H₂O
C H₂O > NH₃ > CH₄
D CH₄ > H₂O > NH₃
Lone pair repulsion reduces bond angle: CH₄ (0 LP) > NH₃ (1 LP) > H₂O (2 LP).
Which species has square planar geometry
A Ni(CO)₄
B XeF₄
C SF₆
D IF₇
XeF₄ has AX₄E₂ arrangement → square planar shape.
Hybridization of central atom in XeF₄ is
A sp³
B sp³d
C sp³d²
D dsp²
Six electron domains (4 bonds + 2 lone pairs) → sp³d² hybridization.
Which compound has the least ionic character
A NaCl
B KCl
C LiCl
D CsCl
Li⁺ is small and highly polarizing → increases covalent character, reducing ionic nature.
Which molecule is non-polar
A NH₃
B H₂O
C CO₂
D SO₂
CO₂ is linear and symmetrical, so bond dipoles cancel.
The bond order of O₂⁻ is
A 1
B 1.5
C 2
D 2.5
O₂ has bond order 2. Adding one electron to antibonding orbital reduces bond order by 0.5.
Which species has highest bond dissociation energy
A O₂
B O₂⁺
C O₂⁻
D O₂²⁻
O₂⁺ has the highest bond order (2.5), hence strongest bond.
Which molecule is paramagnetic
A N₂
B O₂²⁻
C CO
D NO
NO has an odd number of electrons, resulting in one unpaired electron.
Which is isoelectronic with N₂
A O₂
B NO⁺
C CO₂
D O₂⁻
N₂ has 14 electrons. NO⁺ also has 14 electrons.
The stability of a molecule increases with
A Decreasing bond order
B Increasing antibonding electrons
C Increasing bond order
D Increasing bond length
Higher bond order means stronger bond and higher stability.
Which MO is lowest in energy
A σ1s
B σ1s
C π2p
D π2p
Bonding σ1s orbital is the lowest energy MO.
The coordination number of metal in [Fe(C₂O₄)₃]³⁻ is
A 3
B 4
C 6
D 8
Oxalate (C₂O₄²⁻) is bidentate. Three ligands × 2 donor atoms = coordination number 6.
The denticity of oxalate ion is
A 1
B 2
C 3
D 4
Oxalate coordinates through two oxygen atoms → bidentate ligand.
Which complex shows coordination isomerism
A [Co(NH₃)₆]Cl₃
B [Cr(en)₃]Cl₃
C [Co(NH₃)₅Cl]SO₄
D [Co(en)₃][Cr(CN)₆]
Both cation and anion are complex ions → coordination isomerism possible.
Which complex exhibits ionization isomerism
A [Co(NH₃)₅Cl]SO₄
B [Co(NH₃)₆]Cl₃
C [Ni(CO)₄]
D [Zn(NH₃)₄]²⁺
Exchange between coordinated Cl⁻ and counter ion SO₄²⁻ gives ionization isomerism.
Which complex does NOT show geometrical isomerism
A [Pt(NH₃)₂Cl₂]
B [Co(NH₃)₄Cl₂]⁺
C [Cr(en)₂Cl₂]⁺
D [Zn(NH₃)₄]²⁺
Tetrahedral complexes do not show geometrical isomerism.
Which complex shows maximum CFSE (octahedral)
A d⁰
B d³
C d⁵ (high spin)
D d¹⁰
d³ configuration places all three electrons in t₂g orbitals → maximum CFSE.
Which complex is low spin
A [FeF₆]³⁻
B [Fe(CN)₆]³⁻
C [Mn(H₂O)₆]²⁺
D [CoF₆]³⁻
CN⁻ is a strong field ligand → large Δo → electron pairing → low spin.
The number of unpaired electrons in low spin d⁶ octahedral complex is
A 0
B 2
C 4
D 6
Low spin d⁶ fills t₂g completely (t₂g⁶), all electrons paired.
Which metal ion always forms diamagnetic complexes
A Fe²⁺
B Co²⁺
C Zn²⁺
D Ni²⁺
Zn²⁺ has d¹⁰ configuration → no unpaired electrons.
Which ligand increases splitting maximum
A H₂O
B NH₃
C F⁻
D CO
CO is a strong field π-acceptor ligand, producing very large splitting.
The geometry of [Ni(CN)₄]²⁻ is
A Tetrahedral
B Square planar
C Octahedral
D Linear
Ni²⁺ (d⁸) with strong field CN⁻ gives square planar geometry.
Which complex shows fac–mer isomerism
A [Co(NH₃)₆]³⁺
B [Co(NH₃)₄Cl₂]⁺
C [Co(NH₃)₃Cl₃]
D [Pt(NH₃)₂Cl₂]
Octahedral MA₃B₃ complexes exhibit fac and mer isomerism.
The oxidation state of Fe in [Fe(CO)₅] is
A +2
B +3
C 0
D −2
CO is a neutral ligand; the complex is neutral → Fe oxidation state is zero.
Which ligand stabilizes low oxidation states of metals
A F⁻
B H₂O
C CO
D OH⁻
CO is a π-acceptor ligand that stabilizes low oxidation states via back bonding.
Which complex shows back bonding
A [Zn(NH₃)₄]²⁺
B [Ni(CO)₄]
C [Fe(H₂O)₆]²⁺
D [Ag(NH₃)₂]⁺
CO accepts electron density from metal d-orbitals via π back bonding.
Which property explains color of coordination compounds
A Ionic radius
B d–d transitions
C Atomic number
D Coordination number only
Absorption of visible light due to d–d electronic transitions causes color.
Which complex is colorless
A [Cu(H₂O)₆]²⁺
B [Fe(H₂O)₆]³⁺
C [Zn(NH₃)₄]²⁺
D [Ni(H₂O)₆]²⁺
Zn²⁺ is d¹⁰ → no d–d transitions → colorless.
Which coordination number corresponds to octahedral geometry
A 2
B 4
C 5
D 6
Coordination number 6 commonly forms octahedral complexes.
Which complex is paramagnetic
A [Fe(CN)₆]⁴⁻
B [Zn(NH₃)₄]²⁺
C [CoF₆]³⁻
D [Ni(CO)₄]
Co³⁺ with weak field F⁻ remains high spin → unpaired electrons → paramagnetic.
The magnetic moment depends on
A Atomic mass
B Oxidation state only
C Number of unpaired electrons
D Ligand charge only
Spin-only magnetic moment depends on unpaired electrons.
Which complex has coordination number 2
A [Ag(NH₃)₂]⁺
B [Zn(NH₃)₄]²⁺
C [Ni(CO)₄]
D [Co(NH₃)₆]³⁺
Two NH₃ ligands → coordination number 2.
The geometry of [Ag(NH₃)₂]⁺ is
A Bent
B Linear
C Tetrahedral
D Square planar
Coordination number 2 complexes are linear.
Which statement about ligands is correct
A All ligands are negatively charged
B Ligands must be ionic
C Ligands donate lone pair of electrons
D Ligands accept electrons only
Ligands act as Lewis bases, donating electron pairs to metal ions.
The chelate effect is due to
A Enthalpy decrease only
B Entropy increase
C Color formation
D Ionic bonding
Formation of chelate complexes releases more particles → increases entropy → higher stability.
Which ligand forms the most stable chelate
A NH₃
B H₂O
C en
D Cl⁻
en is bidentate and forms stable chelate rings.
Which compound obeys Werner’s theory
A [Co(NH₃)₆]Cl₃
B NaCl
C CaSO₄
D KBr
Werner’s theory explains bonding and ionization in coordination compounds.
Which coordination compound gives 4 ions in solution
A [Co(NH₃)₆]Cl₃
B [Co(NH₃)₅Cl]Cl₂
C [Co(NH₃)₄Cl₂]Cl
D [Co(NH₃)₃Cl₃]
Dissociates into [Co(NH₃)₆]³⁺ + 3Cl⁻ → 4 ions.
Which ligand is ambidentate
A NH₃
B H₂O
C NO₂⁻
D OH⁻
NO₂⁻ can coordinate through N or O atom.
Which complex shows linkage isomerism
A [Co(NH₃)₆]³⁺
B [Co(NH₃)₅NO₂]²⁺
C [Zn(NH₃)₄]²⁺
D [Ni(CO)₄]
NO₂⁻ ligand can bind in two ways → linkage isomerism.
Which metal ion has maximum tendency to form complexes
A Na⁺
B Ca²⁺
C Al³⁺
D K⁺
Small size and high charge favor complex formation.
Which property is NOT explained by crystal field theory
A Color
B Magnetic behavior
C Stability of complexes
D Covalent nature of metal–ligand bond
CFT is purely electrostatic and does not explain covalency.
Which geometry is least common
A Linear
B Tetrahedral
C Octahedral
D Pentagonal bipyramidal
Very few molecules/complexes exhibit pentagonal bipyramidal geometry.
Which metal ion forms colored complexes most readily
A Zn²⁺
B Cu²⁺
C Ca²⁺
D Mg²⁺
Cu²⁺ (d⁹) readily undergoes d–d transitions → colored complexes.
Which complex is low spin and diamagnetic
A [FeF₆]³⁻
B [Fe(H₂O)₆]²⁺
C [Fe(CN)₆]⁴⁻
D [Mn(H₂O)₆]²⁺
Fe²⁺ (d⁶) with strong field CN⁻ gives low spin t₂g⁶ → diamagnetic.
Which statement is correct
A All coordination compounds are colored
B All coordination compounds are paramagnetic
C Coordination compounds may show isomerism
D Coordination compounds contain only ionic bonds
Coordination compounds commonly exhibit various types of isomerism due to ligand arrangement.