The p atom has only three unpaired electrons in its ground state why can it form pcl3

The electron arrangement of the P atom is 3s23p3, and the compounds formed by P and Cl are PCl3 and PCl5, and the P atom has three unpaired electrons in its outermost layer, so it can only combine three Cl atoms to form PCl3.

The P-Cl bonds in the PCl3 molecule are all σ-bonds. -Cl bonds are all σ-bonds, P atoms have three unpaired electrons in the outermost layer, but can form PCl5, indicating that the traditional valence bonding theory is flawed, and the P-Cl bonds in the PCl3 molecule are all π-bonds.