To draw the Lewis structure for phosphoric acid (H3PO4), we first need to count the total number of valence electrons available in the molecule. Hydrogen (H) contributes 1 electron each, phosphorus (P) contributes 5 electrons, and oxygen (O) contributes 6 electrons each. So, the total is:
- 3 H: 3 x 1 = 3 electrons
- 1 P: 5 electrons
- 4 O: 4 x 6 = 24 electrons
Adding these together gives us a total of 3 + 5 + 24 = 32 valence electrons.
Next, we need to arrange these atoms in a way that satisfies the octet rule as closely as possible. We start by placing the phosphorus atom in the center, as it can form multiple bonds. Then, we link it to three hydrogen atoms and four oxygen atoms, one of which will be connected with a double bond to phosphorus. The remaining three oxygen atoms will be single bonded to phosphorus, each carrying a negative charge to satisfy the overall charge of the molecule.
The final Lewis structure can be summarized as follows:
- Phosphorus is surrounded by four oxygen atoms: one with a double bond (P=O) and three with single bonds (P–O).
- Each of the three single-bonded oxygen atoms is then bonded to a hydrogen atom (O–H).
This arrangement yields the correct connectivity and satisfies the valence shell electron configurations for each atom involved. Here’s how the Lewis structure looks:
In the image above, H represents hydrogen atoms, O represents oxygen atoms, and P represents phosphorus. Phosphoric acid plays an important role not only in sodas like Dr Pepper but also in various other applications in food and beverage industries.