How many covalent bonds do you think would form between the phosphorus atoms in the molecule \(\mathrm{P}_{2}\) ? Explain your answer and draw a dot diagram.

Phosphorus is in Group 15 of the periodic table, which means it has 5 valence electrons.

The octet rule states that atoms tend to form covalent bonds in such a way that they achieve an electron configuration similar to that of a noble gas, with a full outer shell containing eight electrons. Since each phosphorus atom has 5 valence electrons, both atoms will need 3 more electrons to achieve a full outer shell. However, when sharing electrons via covalent bonding, each electron being shared gets counted by both atoms in the bond. So if one shared electron pair accounts for two electrons being counted for each atom, then each phosphorus needs to share 1.5 pairs of electrons, or 3. Since bonds have to be whole (no half-bonds), two of the electrons in each atom form a covalent bond. Both atoms will share these electrons so each can achieve 6 valence electrons. If the P-P bond held 3 electron pairs, one phosphorus would be sharing away all 6 valence electrons, which no element does. P may form multiple bonds, but no more than 3 individual bonds and no more than 5 total bond electrons.

To represent this covalent bonding, we will draw a Lewis dot structure. Place a single bond between the two phosphorus atoms and add the remaining three valence electrons for each phosphorus atom as dots around the symbol. The Lewis dot structure for P2 is: :P:::P: In summary, there is one covalent bond between the phosphorus atoms in the molecule P2.