Hey there! For question 24, yes there is. This has to do with the electron configuration of Phosphorus. As you know it has 5 electrons in its valence shell. That's 3s and 3p. You have to fill the s subshell first which contains 1 orbital (2 e- per orbital) so that's 1 pair. Next, you have to fill the 3p subshell which has 3 orbitals but according to Hund's Rule, you have to occupy each orbital first before you can put a second electron in an orbital so those last 3 electrons that we have occupied 1 orbital each so they are unpaired. I hope this helps!