Question

draw the lewis structure for the phosphorus trichloride (pcl₃) molecule.

Explanation:

Step1: Count valence electrons

Phosphorus (P) has 5 valence electrons and each chlorine (Cl) has 7 valence electrons. For $PCl_3$, the total number of valence electrons is $5 + 3\times7=26$.

Step2: Determine the central atom

Phosphorus is the central atom as chlorine is more electronegative.

Step3: Connect atoms with single - bonds

Connect the central P atom to each of the 3 Cl atoms with single bonds (P - Cl). Each single bond uses 2 electrons, so $3\times2 = 6$ electrons are used so far, leaving $26 - 6=20$ electrons.

Step4: Distribute remaining electrons

Distribute the remaining 20 electrons as lone - pairs. Each Cl atom gets 3 lone - pairs (6 electrons per Cl, $3\times6 = 18$ electrons) and the P atom gets 1 lone - pair (2 electrons).

Answer:

The Lewis structure has a central P atom with 1 lone - pair and single bonds to 3 Cl atoms. Each Cl atom has 3 lone - pairs around it.