one way to look at it involves electronegativity. For a bond to be ionic, difference in electronegativity should be greater than 1.7
electronegativity of N is 3.0, and that of hydrogen is 2.2
the difference is less than 1.7
electronegativity of barium is 0.89 and that of bromine is 2.96
the difference is more than 1.7, hence ionic.
more logically, the bond will depend on polarisation. This occurs when a high charge density cation distorts the electron cloud of a large anion. When polarisation occurs, there is sharing of electrons instead of transfer of electrons, hence a covalent bond.
While only looking at electronegativity, other trends come into play as well.
Bromine is atomic number 35, and Barium is 4.
Hydrogen is 1, and Nitrogen is 7. The valence shells around the hydrogen and nitrogen are a lot lesser. Hydrogen bonding is a very strong force. Despite the electronegativities, I believe that the Hydrogen and Nitrogen will be more apt to for an ionic compound.
(Don't count on me though, I'm only 16 and recently started AP Chem.
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