Tetrahedron

• What is a tetrahedral shape?

  A molecular shape where a central atom is bonded to four atoms or groups, arranged at the corners of a tetrahedron, with bond angles of 109.5°.
• Why do molecules adopt a tetrahedral shape?

  The Valence Shell Electron Pair Repulsion (VSEPR) Theory states that electron pairs repel each other and arrange themselves as far apart as possible.
• Name an example of a perfect tetrahedral molecule.

  Methane (CH₄) – Carbon is bonded to four hydrogens, with bond angles of 109.5°.
• How does a perfect tetrahedral shape differ from distorted shapes?

  Perfect tetrahedral: All four bonded groups are identical (e.g., CH₄, bond angle 109.5°). Distorted shapes: Lone pairs cause deviations (e.g., NH₃ has 107°, H₂O has 104.5°).
• Why does ammonia (NH₃) have a trigonal pyramidal shape?

  It has 3 bonding pairs and 1 lone pair. The lone pair repels the bonding pairs more strongly, reducing the bond angle to 107°.
• Why does water (H₂O) have a bent shape?

  It has 2 bonding pairs and 2 lone pairs. The lone pairs push the bonding pairs closer, reducing the bond angle to 104.5°.
• How do lone pairs affect bond angles in tetrahedral shapes?

  Lone pairs repel more strongly than bonding pairs, reducing bond angles: 0 lone pairs: 109.5° (e.g., CH₄). 1 lone pair: 107° (e.g., NH₃). 2 lone pairs: 104.5° (e.g., H₂O).
• What is the shape and bond angle of SiCl₄?

  Perfect tetrahedral with bond angles of 109.5°, as silicon is bonded to four chlorine atoms.
• Why does NH₄⁺ have a perfect tetrahedral shape?

  The nitrogen has 4 bonding pairs and no lone pairs, so the bond angles are 109.5°.
• Why does NH₄⁺ have a perfect tetrahedral shape?

  The nitrogen has 4 bonding pairs and no lone pairs, so the bond angles are 109.5°.