Questions on Coordination Number
20 Multiple-Choice Questions: Coordination Number
Questions
1. What is the coordination number of a central atom in a complex that is bonded to six ligands?
A) 2
B) 3
C) 4
D) 5
E) 6
2. Which of the following correctly defines the coordination number in a complex compound?
A) Number of electrons donated to the metal
B) Number of atoms in the compound
C) Number of metal atoms bonded together
D) Number of ligands directly attached to the central atom
E) Number of ions in solution
3. What is the coordination number of the metal ion in [Cu(NH₃)₄]²⁺?
A) 2
B) 3
C) 4
D) 5
E) 6
4. In a complex ion, what type of bonds are formed between ligands and the central atom?
A) Covalent
B) Ionic
C) Hydrogen
D) Metallic
E) Coordinate covalent
5. Which of the following coordination numbers is most common for transition metal complexes?
A) 1
B) 2
C) 4
D) 8
E) 10
6. The coordination number of Fe in [Fe(CN)₆]³⁻ is:
A) 3
B) 4
C) 5
D) 6
E) 8
7. A complex with coordination number 6 usually exhibits which geometry?
A) Linear
B) Square planar
C) Trigonal planar
D) Tetrahedral
E) Octahedral
8. Which of the following ligands is bidentate?
A) H₂O
B) NH₃
C) CN⁻
D) en (ethylenediamine)
E) Cl⁻
9. In [Co(en)₃]³⁺, what is the coordination number of cobalt?
A) 2
B) 3
C) 4
D) 6
E) 8
10. Which ligand could increase the coordination number most effectively?
A) H₂O
B) en
C) F⁻
D) CN⁻
E) CO
11. What is the coordination number of Zn in [Zn(H₂O)₄]²⁺?
A) 2
B) 3
C) 4
D) 5
E) 6
12. The coordination number of Pt in [PtCl₄]²⁻ is:
A) 2
B) 3
C) 4
D) 5
E) 6
13. Which geometry corresponds to a coordination number of 4?
A) Octahedral
B) Tetrahedral or square planar
C) Trigonal bipyramidal
D) Pentagonal
E) Cubic
14. The coordination number of Ni in [Ni(CO)₄] is:
A) 2
B) 3
C) 4
D) 5
E) 6
15. Which of these has a coordination number of 2?
A) [Ag(NH₃)₂]⁺
B) [Fe(CN)₆]⁴⁻
C) [Co(NH₃)₆]³⁺
D) [Ni(CO)₄]
E) [Cu(en)₂]²⁺
16. The ligand EDTA is:
A) Monodentate
B) Bidentate
C) Tridentate
D) Hexadentate
E) Ambidentate
17. In a crystal lattice, the coordination number refers to:
A) Number of lattice units
B) Number of atoms in a molecule
C) Number of nearest neighbors of a given ion or atom
D) Number of bonds formed per unit cell
E) Number of atoms in one unit
18. What is the coordination number of Cs⁺ in a body-centered cubic structure of CsCl?
A) 4
B) 6
C) 8
D) 10
E) 12
19. A coordination compound contains two bidentate ligands and two monodentate ligands. What is the coordination number?
A) 3
B) 4
C) 5
D) 6
E) 7
20. Which coordination number is typical for a complex showing tetrahedral geometry?
A) 2
B) 3
C) 4
D) 6
E) 8
Answers with Explanations
1. E) 6
→ Coordination number is the number of ligands directly attached to the metal.
2. D) Number of ligands directly attached to the central atom
→ This is the standard definition.
3. C) 4
→ Four NH₃ ligands attached to Cu²⁺.
4. E) Coordinate covalent
→ Ligands donate lone pairs to form coordinate bonds.
5. C) 4
→ Along with 6, it is one of the most common for transition metals.
6. D) 6
→ Six CN⁻ ligands attached to Fe³⁺.
7. E) Octahedral
→ Six ligands arrange themselves octahedrally.
8. D) en (ethylenediamine)
→ It donates two pairs of electrons.
9. D) 6
→ Three bidentate ligands = 6 coordination sites.
10. B) en
→ Bidentate ligands increase coordination per molecule.
11. C) 4
→ Four water molecules coordinate with Zn²⁺.
12. C) 4
→ Four chloride ions coordinate with Pt²⁺.
13. B) Tetrahedral or square planar
→ Both are possible with coordination number 4.
14. C) 4
→ Four CO ligands = tetrahedral geometry.
15. A) [Ag(NH₃)₂]⁺
→ Two ligands = coordination number 2.
16. D) Hexadentate
→ EDTA can bind at six sites.
17. C) Number of nearest neighbors of a given ion or atom
→ Coordination number in crystal lattices refers to nearest neighbors.
18. C) 8
→ Cs⁺ is surrounded by 8 Cl⁻ ions in the BCC structure.
19. D) 6
→ 2 bidentate (2×2) + 2 monodentate = 6 total coordination.
20. C) 4
→ Tetrahedral geometry arises from coordination number 4.
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