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Dative Bonding and Common Examples

Learn and apply Dative Bonding and Common Examples in the published Chemistry course sequence.

  • GCE A-Level H2 Chemistry 9476-2027
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Dative Bonding and Common Examples: Orientation

A dative bond is an exam favourite because the marks are mostly in the arrow direction. If you can reliably identify the donor (lone pair) and acceptor (electron-deficient), you can pick up easy marks.

Treat this as an extension of Atomic Structure (A Level), then use the Chemical Bonding hub to compare models across the topic.

Definitions (Must Know)

A. Dative covalent (coordinate) bond

A dative covalent bond is a covalent bond where both electrons in the shared pair come from the same atom.

B. Electron-pair donor

An electron-pair donor is a species that donates a lone pair to form a dative bond.

C. Electron-pair acceptor

An electron-pair acceptor is a species that accepts a lone pair to form a dative bond.

Detailed Explanations

A. Donor vs acceptor (how to spot them)

  • Donor: has a lone pair on the atom that will bond (often N/O/halide ions).
  • Acceptor: electron-deficient or positively charged (can accept a lone pair into an empty orbital).

In NH₃ + H⁺ → NH₄⁺, N has a lone pair (donor) and H⁺ has no electrons (acceptor).

B. How to draw a dative bond (workflow)

  1. Identify the donor atom (where the lone pair is).
  2. Identify the acceptor atom (electron-deficient/positive).
  3. Draw the arrow from donor to acceptor (this arrow shows where the shared pair came from).
  4. Check overall charge after forming the bond.

For NH₃ + H⁺ → NH₄⁺, draw the arrow from N to H and place the product in brackets with overall charge + 1.

Ammonia's single nitrogen lone pair donated along a curved arrow to a hydrogen ion, a separate reaction arrow to the bracketed ammonium ion with one N to H bond drawn as an arrow, and aluminium chloride dimer with each bridging chlorine drawing a dative arrow to the other aluminium atom
The curved arrow shows the nitrogen lone pair being donated to H⁺; the black arrow is the overall reaction. A bond arrow points from the atom that supplied the shared pair to the acceptor. It records the pair's origin only: all four N–H bonds in NH₄⁺ are identical.

C. Common examples you must recognise

  • NH₃ + H⁺ → NH₄ +
  • Al₂Cl₆ contains dative bonds from Cl lone pairs to electron-deficient Al centres.

What to say for Al₂Cl₆:

  • AlCl₃ is electron-deficient (Al has an incomplete octet).
  • One terminal Cl from each AlCl₃ unit donates a lone pair to the Al atom in the other unit.
  • The product has two bridging Cl atoms and two dative bonds in total—not four.

Worked Examples

Modelled example 1

Identify the Donor in Ammonium Formation

Core

Problem

In the formation of NH₄ + from NH₃ and H⁺, which species donates the electron pair?

Study the worked solution

  1. Find the available lone pair

    Method

    Identify the lone pair on nitrogen in NH₃.

    Reason

    A dative-bond donor supplies both electrons in the new shared pair.

    Working

    :NH₃ is the electron-pair donor.

  2. Identify the acceptor

    Method

    Identify H⁺ as electron-deficient.

    Reason

    The proton can accept the nitrogen lone pair.

    Working

    H⁺ is the electron-pair acceptor.

  3. State the donation direction

    Method

    Direct the pair from nitrogen to the proton.

    Reason

    The arrow follows the electron pair from donor to acceptor.

    Working

    NH₃ → H⁺ forms NH₄ +.

Guided practice 2

Complete the Ammonium Formation Diagram

About 6 min

Problem

Describe the three features that a diagram of NH₃ + H⁺ → NH₄ + must show to represent the dative bond unambiguously.

Try this before viewing the solution

Hints

Hint 1: start at the donor
Show the nitrogen lone pair before bond formation.
Hint 2: finish the product
The arrow points to H, and the complete product has an overall + 1 charge.
View solution step by step

  1. Show the donated pair

    Method

    Draw the lone pair on nitrogen in NH₃.

    Reason

    Both electrons in the new bond originate from nitrogen.

    Working

    :NH₃

  2. Direct the arrow

    Method

    Draw the arrow from N to H⁺.

    Reason

    The arrow records electron-pair donation from donor to acceptor.

    Working

    N → H⁺

  3. Show the product charge

    Method

    Place the ammonium product in brackets with overall charge + 1.

    Reason

    The product contains the incoming proton and remains a cation.

    Working

    [NH₄]⁺

Common misconception 3

Correct a Reversed Dative Arrow

Find and correct the mistake

Learner attempt

A learner draws the ammonium-formation arrow from H⁺ towards N because “the proton moves towards ammonia.” Identify the error and correct the arrow direction.

Follow the electron pair

Dative arrow direction

View solution step by step

  1. Identify what the arrow represents

    Method

    Treat the arrow as electron-pair movement, not nuclear motion.

    Reason

    The donor is defined by supplying both bonding electrons.

    Working

    Nitrogen supplies the lone pair.

  2. Correct the direction

    Method

    Draw the arrow from N to H⁺.

    Reason

    NH₃ is the donor and H⁺ is the acceptor.

    Working

    N → H⁺

Examiner practice 4

Analyse the Aluminium Chloride Dimer

4 marks

Problem

How many dative bonds and bridging chlorine atoms are present in Al₂Cl₆? State the donor and acceptor. [4 marks]

Try this before viewing the solution

View solution step by step

  1. Count the bridges

    1 mark

    Method

    Identify the two chlorine atoms shared between the aluminium centres.

    Reason

    These are the bridging chlorine atoms in the dimer.

    Working

    Two bridging Cl atoms.

  2. Count the dative bonds

    1 mark

    Method

    Count one donation across each reciprocal bridge.

    Reason

    Each AlCl₃ unit supplies one donor chlorine to the other unit.

    Working

    Two dative bonds in total.

  3. Identify the donor

    1 mark

    Method

    Name chlorine as the electron-pair donor.

    Reason

    A lone pair on a bridging chlorine supplies the shared pair.

    Working

    Donor: Cl in one AlCl₃ unit.

  4. Identify the acceptor

    1 mark

    Method

    Name aluminium in the other unit as acceptor.

    Reason

    The aluminium centre is electron-deficient and accepts the lone pair.

    Working

    Acceptor: Al in the other AlCl₃ unit.

Challenge 5

Interpret the Bonds after Ammonium Forms

Minimal support

Problem

A diagram marks one N–H bond in NH₄ + as having formed by lone-pair donation. A learner concludes that this bond remains a different, automatically weaker type of bond than the other three N–H bonds. Evaluate the conclusion.

Try this before viewing the solution

Hints

Hint 1: separate formation from the product
The arrow records where the shared pair originated during formation.
Hint 2: classify the formed bond
Once formed, a dative bond is treated as an ordinary covalent bond.
View solution step by step

  1. Interpret the arrow correctly

    Method

    Use it to identify the original electron-pair donor.

    Reason

    The arrow is a record of bond formation, not a permanent label of weaker electrons.

    Working

    The marked pair originally came from nitrogen.

  2. Evaluate the product bonds

    Method

    Reject the claim that the donated-pair bond remains automatically weaker or distinct.

    Reason

    After formation it is a covalent N–H bond and is treated like the other N–H bonds in NH₄ +.

    Working

    The four N–H bonds in ammonium are equivalent.

Mind Stretchers

Mind stretcher 1Extension

Explain why AlCl₃ forms Al₂Cl₆ and identify the donor and acceptor in the dative bond.

Show Answer

Mark scheme:

  • In AlCl₃, Al is electron-deficient (does not have a full octet).
  • A lone pair on Cl can be donated into an empty orbital on Al to form a dative bond.
  • Donor: a Cl atom (lone pair). Acceptor: Al in AlCl₃.
  • Dimer formation increases the electron count around Al (more stable structure).