what type of bonding is phosphoric acid?
Mostly covalent
isn't it also ionic bonds too with the hydrogen ions? i don't really understand it
I know it's a bit late. I could be wrong, but I'm fairly sure it's hydrogen bonding.
Phosphoric acid, which has the chemical formula H3PO4, is an example of a molecule that exhibits both covalent and ionic bonding. The bonding in phosphoric acid can be understood by examining its Lewis structure.
To determine the bonding in phosphoric acid, you need to draw its Lewis structure by following these steps:
Step 1: Count the total number of valence electrons in phosphoric acid. Phosphorus (P) is in Group 5 of the periodic table, so it has 5 valence electrons. Each oxygen (O) atom has 6 valence electrons, and there are 4 oxygen atoms in phosphoric acid. Finally, hydrogen (H) has 1 valence electron, and there are 3 hydrogen atoms. Therefore, the total number of valence electrons is: 5 + 4(6) + 3(1) = 32.
Step 2: Determine the central atom. In phosphoric acid, the central atom is phosphorus (P) since it is less electronegative than oxygen (O).
Step 3: Connect all atoms using single bonds. Each bond consists of a pair of electrons, so these shared electron pairs form covalent bonds between the atoms. Start by connecting each oxygen atom to the central phosphorus atom with a single bond, and fill in their remaining valence electrons. This step will require eight electrons in total.
Step 4: Distribute the remaining electrons to satisfy the octet rule, except for hydrogen. Place them around the oxygen atoms, keeping in mind that each oxygen atom wants to have a total of 8 electrons around itself (except for hydrogen, which only needs 2 electrons for a full outer shell). Distribute the remaining 24 electrons in this way.
Step 5: Place any remaining electrons on the central atom. In this case, phosphorus (P) has no remaining electrons.
Step 6: Determine the formal charge on each atom if necessary. The formal charge is the difference between the valence electrons of an atom in its free state and the number of electrons associated with it in the Lewis structure. If you need to, assign formal charges to each atom to ensure they sum to the total charge of the molecule (+1 in the case of phosphoric acid).
After completing these steps, you will have a Lewis structure for phosphoric acid. The structure reveals that the bond between phosphorus and each oxygen atom is covalent, involving the sharing of electrons. On the other hand, the bond between phosphorus and each hydrogen atom is purely ionic since the electronegativity difference between phosphorus and hydrogen is significant.
In summary, phosphoric acid exhibits both covalent bonding between phosphorus and oxygen atoms and ionic bonding between phosphorus and hydrogen atoms.