Questions on Covalent Bonding in Polyatomic Ions
Multiple-Choice Questions: Covalent Bonding in Polyatomic Ions
1. What type of bonding is found within polyatomic ions?
A) Ionic only
B) Metallic
C) Covalent
D) Hydrogen bonding
E) Ionic and metallic
2. What is a polyatomic ion?
A) A single atom with a positive charge
B) A molecule with unshared electron pairs
C) A charged group of covalently bonded atoms
D) A neutral diatomic molecule
E) An ion formed from a metal
3. Which of the following is a polyatomic ion?
A) Na⁺
B) OH⁻
C) Cl⁻
D) H₂
E) O₂
4. What kind of bond holds the atoms together in a polyatomic ion like NO₃⁻?
A) Ionic
B) Covalent
C) Metallic
D) Coordinate
E) Van der Waals
5. Which of these polyatomic ions contains a double bond in its covalent structure?
A) NH₄⁺
B) OH⁻
C) NO₃⁻
D) CN⁻
E) SO₄²⁻
6. In the sulfate ion (SO₄²⁻), how many oxygen atoms are bonded to sulfur?
A) 1
B) 2
C) 3
D) 4
E) 5
7. Which element acts as the central atom in the ammonium ion (NH₄⁺)?
A) H
B) O
C) N
D) C
E) Na
8. Which polyatomic ion contains a coordinate covalent bond?
A) SO₄²⁻
B) PO₄³⁻
C) NH₄⁺
D) NO₃⁻
E) ClO₄⁻
9. How many total valence electrons are used in the Lewis structure of NO₃⁻?
A) 23
B) 24
C) 32
D) 18
E) 16
10. What is the charge on the carbonate ion?
A) 0
B) 1⁺
C) 1⁻
D) 2⁻
E) 3⁻
11. Which of the following is the correct formula for the phosphate ion?
A) PO₂⁻
B) P₃O₄³⁻
C) PO₄³⁻
D) PO₃²⁻
E) P₂O₇²⁻
12. How many covalent bonds are present in the ammonium ion (NH₄⁺)?
A) 1
B) 2
C) 3
D) 4
E) 5
13. Which of the following best describes the bonding in the hydroxide ion (OH⁻)?
A) Ionic bond between O and H
B) Covalent bond with one extra electron
C) Hydrogen bond with water
D) Coordinate bond from O to H
E) Metallic bonding
14. What is the formal charge on nitrogen in the nitrate ion (NO₃⁻)?
A) 0
B) +1
C) +2
D) -1
E) -2
15. How many covalent bonds are typically formed by oxygen in polyatomic ions?
A) 1
B) 2
C) 3
D) 4
E) 5
16. Which of these ions contains three resonance structures?
A) NH₄⁺
B) CO₃²⁻
C) OH⁻
D) NO₃⁻
E) SO₄²⁻
17. In the carbonate ion (CO₃²⁻), how many oxygen atoms are singly bonded to carbon?
A) 1
B) 2
C) 3
D) 0
E) None—only double bonds exist
18. The bonds in a polyatomic ion like SO₄²⁻ are described as:
A) Ionic
B) Unequal polar bonds
C) Equal covalent bonds due to resonance
D) Van der Waals forces
E) Dispersive forces
19. Which of the following ions is linear in shape due to covalent bonding?
A) CO₃²⁻
B) NO₂⁻
C) NH₄⁺
D) CN⁻
E) SO₃²⁻
20. Why are resonance structures used in polyatomic ions?
A) To show ionic bonding possibilities
B) To indicate unstable compounds
C) To represent delocalized electrons in covalent bonds
D) To visualize magnetic fields
E) To distinguish between isomers
Answers with Explanations
1. C) Polyatomic ions contain covalent bonds between atoms.
2. C) A polyatomic ion is a charged group of covalently bonded atoms.
3. B) OH⁻ (hydroxide) is a classic polyatomic ion.
4. B) Covalent bonds hold atoms together within the ion.
5. C) NO₃⁻ has resonance with one double bond at a time.
6. D) In SO₄²⁻, four oxygen atoms are bonded to sulfur.
7. C) Nitrogen is the central atom in NH₄⁺.
8. C) In NH₄⁺, one bond is formed by donation of a lone pair (coordinate bond).
9. B) 5 (N) + 3×6 (O) + 1 (extra electron) = 24 valence electrons.
10. D) The carbonate ion has a 2⁻ charge.
11. C) PO₄³⁻ is the correct formula for the phosphate ion.
12. D) NH₄⁺ has four covalent bonds (N-H).
13. B) OH⁻ has a covalent O-H bond with one extra electron (giving the ion a charge).
14. A) The formal charge on nitrogen in NO₃⁻ is typically 0 due to resonance distribution.
15. B) Oxygen usually forms two covalent bonds.
16. D) NO₃⁻ has three resonance structures.
17. C) All three oxygens are equivalent due to resonance—each has partial single/double bond character.
18. C) SO₄²⁻ has equivalent covalent bonds due to resonance.
19. D) CN⁻ is a linear ion with a triple bond.
20. C) Resonance structures show delocalized electrons across multiple bonds.
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