The choices that should have accompanied this question were: A. 1 <span>B. 2 </span> <span>C. 3 </span> <span>D. 4 </span> My answer is B. 2. Below is an explanation, I found while doing the research.
<span>Phosphate needs 3 electrons each totaling 6 electrons so each zinc will need to give up 2 electrons.
Phosphate wants to imitate the electron configuration of Argon because noble configurations are the most stable. With P getting the extra electrons the valence shell will be 3s2 3p6, which is the same as Argon. Without the extra electrons, the P valence shell looks like this 3s2 3p3, now you can see why each phosphorus wants 3 more electrons, that will make it 3s2 3p6, just like Argon.</span>
As the phosphorus has 5 valence electrons, in the first layer it has 2, so the ones it combines are 3. In total there are 6 negative phosphorus charges because they are two phosphorus atoms. The number of Zinc atoms is 3 so to balance the loads, you have to have +2 so that in total there are 6 charges.