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Difficulty: MediumCovalent and Dative (Coordinate) Bonding

Which of the following chemical species contains both covalent and dative (coordinate) covalent bonds?

  1. Ammonium ion (NH4+NH_4^+)Answer
  2. B
    Methane (CH4CH_4)
  3. C
    Sodium chloride (NaClNaCl)
  4. D
    Water (H2OH_2O)

Answer

Ammonium ion (NH4+NH_4^+) contains three covalent bonds and one dative (coordinate) covalent bond.
The ammonium ion (NH4+NH_4^+) is formed when a neutral ammonia molecule (NH3NH_3), which has three single covalent bonds and one unshared lone pair on the nitrogen atom, donates its lone pair of electrons to an electron-deficient hydrogen ion (H+H^+). Therefore, NH4+NH_4^+ contains both three standard covalent bonds and one dative bond.

Step-by-Step Solution

1
Analyze the electronic configuration and bonding of ammonia (NH3NH_3)
In NH3NH_3, the central nitrogen atom forms 3 covalent bonds with hydrogen atoms, sharing three of its valence electrons, leaving one unshared lone pair of electrons.
Understanding the starting structure is essential to see where the unshared electron pair originates.
2
Examine the reaction of ammonia with a hydrogen ion (H+H^+)
The hydrogen ion (H+H^+) has an empty 1s1s orbital and requires two electrons to achieve a stable duplet configuration.
A dative bond requires an electron donor (species with a lone pair) and an electron acceptor (species with an empty orbital).
3
Determine the bond types in NH4+NH_4^+
Nitrogen donates its lone pair to the incoming H+H^+ ion forming a coordinate bond, while retaining the three original covalent bonds.
This confirms the co-existence of 3 ordinary covalent bonds and 1 dative bond within the ammonium ion.

Key Concept

Covalent and Coordinate (Dative) Bonding in Polyatomic Ions
Estimated Time:1m 0s
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Topics

Covalent and Dative (Coordinate) Bonding

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