Why The Bond Angle Of Methane Is 109 Instead Of 90?

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Why the bond angle of methane is 109 instead of 90?

• Thread starter Thread starter scientist91
• Start date Start date Apr 30, 2007
• Tags Tags Angle Bond Methane

Click For Summary

Discussion Overview

The discussion centers on the bond angle of methane, specifically why it is approximately 109.5 degrees rather than 90 degrees. Participants explore the implications of molecular geometry, hybridization, and the stability of the molecule.

Discussion Character

• Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

• One participant notes that sp3 hybrid orbitals form a bond angle of 109.5 degrees and questions whether this angle minimizes repulsion.
• Another participant suggests that the initial inquiry may stem from a two-dimensional perspective and questions the validity of the orbital theory being used.
• A third participant emphasizes that in three-dimensional space, four points arranged around a center form a tetrahedron, leading to the bond angle of 109.5 degrees.
• A fourth participant explains that methane has four bonded pairs (C-H bonds) and adopts a tetrahedral shape to minimize repulsion, arguing that a bond angle of 90 degrees would result in instability.

Areas of Agreement / Disagreement

Participants present multiple viewpoints regarding the geometry and stability of methane, with no consensus reached on the initial question of bond angles.

Contextual Notes

Some assumptions about orbital theory and molecular geometry are not explicitly stated, and the discussion does not resolve the implications of different theoretical approaches.

scientist91 Messages 133 Reaction score 0 I know that the sp3 hybrid orbitals form 109 angle, but why the angle is not 90. If the angle is 109 the repulsion is minimized or what? Show some comparations. Thank u. Chemistry news on Phys.org

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sicjeff Messages 46 Reaction score 0 I believe your problem lies in the fact that you are only looking in two dimensions. What orbital theory are you using? Valence shell theory is useless for all practical applications anyway. Andronicus1717 Messages 32 Reaction score 1 3 Dimensions Indeed, in 3d space four points equally spaced around a center point form a tetrahedron, not a square, hence your bond angle of 109.5 degrees. Kushal Messages 438 Reaction score 1 methane consists of four bonded pairs, i.e 4 C-H bonds. So as to minimize repulsion, the molecule adopts a tetrahedral shape, hence bond angle becomes 109.5. with bond angle of 90, the molecule would not be very stable.

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