What is the Lewis Structure for P4, its electron geometry, and molecular geometry?
The Correct Answer and Explanation is :
The Lewis structure for P₄ (tetraphosphorus) can be drawn as follows:
- Count the valence electrons: Phosphorus (P) is in Group 15 of the periodic table, so it has 5 valence electrons. For P₄, this gives a total of ( 4 \times 5 = 20 ) valence electrons.
- Construct the skeleton: Place the four phosphorus atoms in a tetrahedral arrangement since they will be bonded to each other. Start by connecting the phosphorus atoms with single bonds. Each single bond represents two electrons, so using 3 single bonds accounts for 6 electrons.
- Distribute remaining electrons: After placing the single bonds, we have ( 20 – 6 = 14 ) electrons left to place. Distribute the remaining electrons as lone pairs around the phosphorus atoms. Each phosphorus atom needs 8 electrons in its valence shell to follow the octet rule. Phosphorus, being in period 3 of the periodic table, can expand its valence shell, so it can accommodate more than 8 electrons, allowing for double bonds if needed.
- Create double bonds: The final structure of P₄ includes three single bonds and one lone pair per phosphorus atom, with each phosphorus atom forming a single bond to two other phosphorus atoms. This configuration satisfies the valence electron count and minimizes lone pairs.
Electron Geometry:
The electron geometry of P₄ is tetrahedral. This is because each phosphorus atom is surrounded by three regions of electron density (two single bonds and one lone pair). In the case of tetrahedral molecules, the electron pairs will arrange themselves as far apart as possible.
Molecular Geometry:
The molecular geometry of P₄ is trigonal pyramidal. This is due to the lone pair on each phosphorus atom. Since lone pairs take up more space than bonding pairs, they influence the molecular geometry by pushing the bonded atoms closer together, creating a trigonal pyramidal shape.
In summary:
- Lewis Structure: A tetrahedral arrangement with 3 single bonds and lone pairs on each phosphorus atom.
- Electron Geometry: Tetrahedral.
- Molecular Geometry: Trigonal pyramidal.