How to Draw the Lewis Dot Structure for Phosphorus Trihydride

To draw the Lewis dot structure for phosphorus trihydride (PH₃), follow these steps:

1. Determine the total number of valence electrons:
   • Phosphorus (P) has 5 valence electrons.
   • Each hydrogen (H) atom has 1 valence electron.
   • Since there are 3 hydrogen atoms, the total number of valence electrons is 5 + (3 × 1) = 8.
2. Identify the central atom:
   • Phosphorus is the central atom because it is less electronegative than hydrogen.
3. Draw the skeletal structure:
   • Place the phosphorus atom in the center and arrange the three hydrogen atoms around it.
4. Distribute the electrons:
   • Place a single bond (represented by a line) between the phosphorus atom and each hydrogen atom. This uses 6 of the 8 valence electrons.
   • The remaining 2 electrons are placed as a lone pair on the phosphorus atom.
5. Check the octet rule:
   • Phosphorus has 8 electrons around it (6 from the bonds and 2 from the lone pair), satisfying the octet rule.
   • Each hydrogen atom has 2 electrons, which is also stable.

Here is the final Lewis dot structure for PH₃:

    H
    |
H—P—H
    |
    H

This structure shows the arrangement of atoms and the distribution of electrons in phosphorus trihydride.