Formal Charge on O-atom:
To determine the formal charge on the oxygen atom in the PO4^3- ion, we need to consider the valence electrons and the number of bonds formed by the oxygen atom in the molecule.

- Oxygen is in Group 6 of the periodic table, so it has six valence electrons.
- In the PO4^3- ion, there are four oxygen atoms bonded to the central phosphorus atom.
- Each oxygen atom forms a single bond with the phosphorus atom, resulting in a total of four bonds.

To calculate the formal charge on the oxygen atom, we use the formula:
Formal Charge = Valence Electrons - (Lone Pair Electrons + 1/2 * Bonding Electrons)

In the case of the oxygen atom in the PO4^3- ion:
Valence Electrons = 6
Lone Pair Electrons = 6 (since oxygen has formed four single bonds, it has two lone pairs)
Bonding Electrons = 4 (since there are four oxygen atoms bonded to the phosphorus atom)

Formal Charge = 6 - (6 + 1/2 * 4) = 6 - (6 + 2) = 6 - 8 = -2

Therefore, the formal charge on the oxygen atom in the PO4^3- ion is -2.

P-O Bond Order:
The bond order represents the number of chemical bonds between two atoms. To determine the bond order between the phosphorus and oxygen atoms in the PO4^3- ion, we need to analyze the Lewis structure.

- In the Lewis structure of the PO4^3- ion, the phosphorus atom is surrounded by four oxygen atoms, each forming a single bond.
- The Lewis structure of PO4^3- can be represented as:

O O
\ /
P
/ \
O O

- In the Lewis structure, there are four single bonds between the phosphorus and oxygen atoms.

The bond order is calculated by counting the number of bonds and dividing it by the number of bond groups. Since there are four bonds between the phosphorus and oxygen atoms and only one bond group, the bond order is:

Bond Order = Number of Bonds / Number of Bond Groups = 4 / 1 = 4

Therefore, the bond order between the phosphorus and oxygen atoms in the PO4^3- ion is 4.

Bond order is 1.25, Formal charge on oxygen is -3/4