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BRIDGE BONDING · ADVANCED CONCEPT

Be₂H₄
Beryllium hydride bridge bonding

Vapour-phase BeH₂ can dimerise as Be₂H₄ through two hydrogen bridges. Because bridging hydrogen has no lone pair to donate, each Be–H–Be unit uses one shared electron pair across three nuclei.

3c–2e hydrogen bridgeChemical BondingInteractive 3D lab
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STRUCTURE REASONING

How Be₂H₄ bridge bonding works.

The two electron-poor beryllium centres are linked by two simultaneous hydrogen bridges. The classroom orbital picture aligns a hydrogen 1s orbital between approximately sp²-directed orbitals on Be, producing a 3c–2e unit rather than two separate ordinary Be–H bonds.

BOND COUNT

2 × 3c–2e bridges + 2 × terminal 2c–2e Be–H bonds

TERMINAL VS BRIDGE

Each bridge Be–H contact is weaker than a terminal Be–H bond.

ADVANCED CONCEPT CHECKLIST

Facts to read from the 3D model.

  1. Both hydrogen bridges form together and must be counted as two multicentre units.
  2. The complete six-atom Be₂H₄ model is planar in this representation.
  3. The displayed bridge angle is approximately 108° in the 3D model.
  4. Be₂H₄ and B₂H₆ are both 3c–2e systems, but their numbers of terminal bonds differ.

SEARCHED QUESTIONS

Be₂H₄ bridge-bonding FAQ.

What type of bridge bond occurs in Be2H4?

Be₂H₄ contains two three-centre two-electron Be–H–Be hydrogen bridges.

Why is Be2H4 electron deficient?

The available valence electrons are insufficient to describe every Be–H contact as an independent ordinary 2c–2e bond, so electron pairs are shared through multicentre bridges.

Is Be2H4 planar?

The complete Be₂H₄ dimer is shown as a planar six-atom structure in the simulation model.

MOLECULE-BY-MOLECULE GUIDES

Study every bridge-bonding system.

Open a focused structure guide, then use the shared 3D lab to rotate the complete molecule and compare bridge formation.