What is the AXE notation of

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What is the AXE notation of…
1) IBr-
2) C2H2
3) NO-
4) AIF3
5) NOH3
6) Si2I4

The Correct Answer and Explanation is :

AXE Notation and Explanation

The AXE notation is used in the Valence Shell Electron Pair Repulsion (VSEPR) theory to determine the molecular geometry of a compound. It is represented as AX(_m)E(_n), where:

  • A: Central atom.
  • X(_m): Number of bonded atoms to the central atom.
  • E(_n): Number of lone pairs on the central atom.

Answers

  1. IBr(^-): AX(_2)E(_3)
  • Iodine (I) is the central atom, bonded to one bromine atom and has 3 lone pairs of electrons. The extra negative charge adds to the lone pairs.
  • Molecular shape: Linear.
  1. C(_2)H(_2): AX(_2)
  • Each carbon atom forms a triple bond with the other carbon and a single bond with one hydrogen. There are no lone pairs on either carbon.
  • Molecular shape: Linear.
  1. NO(^-): AXE(_2)
  • Nitrogen (N) is the central atom, bonded to oxygen and has two lone pairs. The negative charge adds to the lone pairs.
  • Molecular shape: Linear.
  1. AlF(_3): AX(_3)
  • Aluminum (Al) is the central atom, bonded to three fluorine atoms, with no lone pairs.
  • Molecular shape: Trigonal planar.
  1. NOH(_3): AX(_4)
  • Nitrogen (N) is the central atom, bonded to three hydrogens and one hydroxyl group (-OH). There are no lone pairs.
  • Molecular shape: Tetrahedral.
  1. Si(_2)I(_4): AX(_4)
  • Each silicon (Si) atom is bonded to two iodine atoms and one silicon atom, with no lone pairs.
  • Molecular shape: Tetrahedral for each Si center.

Explanation (300 Words)

The VSEPR theory is based on the repulsion between electron pairs (bonding and non-bonding) surrounding a central atom. The AXE notation simplifies the classification of molecular geometries by counting bonded atoms (X) and lone pairs (E) around the central atom (A).

For each molecule:

  1. IBr(^-): Iodine has 7 valence electrons, bonds with bromine, and receives an extra electron due to the negative charge. This results in a total of 10 valence electrons, distributed as one bond and three lone pairs.
  2. C(_2)H(_2): Each carbon has 4 valence electrons, forms a triple bond between them, and single bonds with hydrogen, yielding a linear geometry.
  3. NO(^-): Nitrogen has 5 valence electrons, bonds with oxygen, and gains one electron from the negative charge. This results in two lone pairs and one bond.
  4. AlF(_3): Aluminum has 3 valence electrons, bonds to three fluorines, and has no lone pairs, resulting in trigonal planar geometry.
  5. NOH(_3): Nitrogen bonds with three hydrogens and an -OH group, with no lone pairs, forming a tetrahedral shape.
  6. Si(_2)I(_4): Silicon bonds with iodine and silicon, forming tetrahedral geometries at each silicon center due to no lone pairs.

This approach aligns molecular shapes with electron pair distributions.

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