## Chemistry: An Atoms-Focused Approach

(a) hydrofluoric acid (b) bromic acid (c) H$_3$PO$_4$ (d) HNO$_2$
(a) hydrofluoric acid When naming an acid between hydrogen and an element in group 17, we add the prefix $hydro-$ to the name of the halogen, change the ending of the halogen to $-ic$, and add the word "acid" at the end. (b) bromic acid For acids made with oxoanions, we take the name of the oxoanion (bromate, in this case), remove the $-ate$ ending and replacing it with $-ic$, and then adding the word "acid" to the end. (c) H$_3$PO$_4$ This acid is made with hydrogen combined with the phosphate ion (PO$_4$$^{3-}), which is an oxoanion; therefore, the ending of the oxoanion was changed to -ic. Because the hydrogen ion has a valence of 1+ and the phosphate ion has a valence of 3-, we need three hydrogen atoms for every phosphate ion to balance the charges in the compound. (d) HNO_2 This acid is made with hydrogen combined with the nitrite ion (NO_2$$^{1-}$), which is an oxoanion; therefore, the ending of the oxoanion was changed to $-ic$. Because the hydrogen ion has a valence of 1+ and the nitrite ion has a valence of 1-, we need one hydrogen atom for every nitrite ion to balance the charges in the compound.