back bonding

Which of the following statement (s) is/are correct? (a)In BF_3 , there is pπ-pπ back bonding B and F. (b)In BI_3 , there is pπ-pπ back bonding B and I . (c) pπ-pπ back bonding makes BI_3 least acidic among boron trihalides. (d) BI_3 is strongest Lewis acid among all the boron trihalides.

Which of the following statement (s) is/are correct? (a)In BF_3 , there is pπ-pπ back bonding B and F. (b)In BI_3 , there is pπ-pπ back bonding B and I (c) pπ-pπ back bonding makes BI_3 least acidic among boron trihalides. (d) BI_3 is strongest Lewis acid among all the boron trihalides.

The number of oxygen atoms in borax which do not from ppi-ppi back bond is:

The number of oxygen atoms in borax which do not from ppi-ppi back bond is: