Whats the question ? all you said was she pumps up a soccer ball
PO4 anion has a 3- charge.A sodium cation , has a 1+ charge.Now , you have to think how many Na ions you need to fully neutralize the PO4 's 3- charge. Answer 3. That's because a molecule must have a neutral charge (a 0 charge). 3+(-3)=0.So , sodium phosphate has the formula Na3PO4.
<span>Net Ionic equation: 3Zn^2+(aq) + 2PO4^3-(aq) ---> Zn3(PO4)2 (s)
hope it helps
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Lithium i believe is the answer