Introduction:
(ClO3)^- is a polyatomic ion also known as chlorate ion. It is composed of one chlorine atom and three oxygen atoms. The bond order between Cl and O atoms in the chlorate ion can be calculated using molecular orbital theory.

Molecular Orbital Theory:
Molecular orbital theory is a model used to describe the bonding between atoms in a molecule. The theory assumes that atomic orbitals combine to form molecular orbitals, which are shared by the atoms in the molecule.

Bond Order:
Bond order is the number of chemical bonds between a pair of atoms. It can be calculated using the formula:

Bond order = (Number of bonding electrons - Number of anti-bonding electrons) / 2

Calculation of Bond Order:
In (ClO3)^-, the chlorine atom is sp^3 hybridized and is surrounded by four electron pairs. Three of these electron pairs are shared with three oxygen atoms, while the fourth electron pair is a non-bonding lone pair.

The molecular orbital diagram for (ClO3)^- can be drawn as follows:

The valence electrons of chlorine and oxygen atoms are placed in the molecular orbitals according to their energy levels. The bonding orbitals are lower in energy than the anti-bonding orbitals. The bond order between Cl and O atoms can be calculated by counting the number of bonding and anti-bonding electrons.

Number of bonding electrons = 6
Number of anti-bonding electrons = 2

Bond order = (6 - 2) / 2 = 2

Conclusion:
The bond order between Cl and O atoms in (ClO3)^- is 2. This indicates that there are two chemical bonds between the chlorine atom and each oxygen atom in the chlorate ion.