In BrO3-, the central bromine atom is bonded to three oxygen atoms. The bromine atom has one lone pair of electrons.
The Lewis structure of BrO3- shows that there are three single bonds between the bromine atom and each oxygen atom. Therefore, there are three sigma bonds in BrO3-.
Each oxygen atom has two lone pairs and one single bond, which means that each oxygen atom has one pi bond. Therefore, there are three pi bonds in BrO3-.
The formal charge on the bromine atom in BrO3- is +1. Each oxygen atom has a formal charge of -1. To calculate the total number of sigma bonds and pi bonds, we need to consider the number of valence electrons in the molecule.
The total number of valence electrons in BrO3- is:
7 (valence electrons of bromine) + 3x6 (valence electrons of each oxygen atom) + 1 (charge) = 26
Each single bond contributes two electrons to the total count, while each pi bond contributes four electrons.
The three single bonds in BrO3- contribute 6 electrons to the total count, while the three pi bonds contribute 12 electrons.
Therefore, there are 3 sigma bonds and 3 pi bonds in BrO3-.