On the Lewis structure of phosphoric acid
Phosphoric acid, its chemical formula is $H_3PO_3 $, which is of great significance for Lewis structure analysis.
When constructing the Lewis structure of phosphoric acid, the number of valence electrons of each atom must be determined first. Phosphorus ($P $) is located in group V $A $, and its valence electrons are 5 dollars $; oxygen ($O $) is located in group VI $A $, and the valence electrons are 6 dollars $; hydrogen ($H $) has a valence electron number of 1 dollar $. Then the total valence electrons of $H_3PO_3 $are: 3 dollars\ times1 + 5 + 3\ times6 = 26 $.
Usually, in the Lewis structure, the phosphorus atom is the central atom. Because phosphorus atoms can form multiple chemical bonds, and the electronegativity is relatively small. With the phosphorus atom as the core, three hydroxyl groups ($-OH $) are connected to the phosphorus atom, so that 3 dollars\ times2 = 6 $electrons (each $P-O $bond uses 2 dollars $electrons), while the three hydrogen atoms are connected to the three oxygen atoms respectively, and 3 dollars\ times2 = 6 $electrons. At this point, there are 26 dollars - 6 - 6 = 14 $electrons left.
The remaining electrons are allocated to the oxygen atom and the phosphorus atom to satisfy the octet rule (the hydrogen atom satisfies the 2 dollars $electron stability structure has been achieved). In the phosphorus structure, a double bond is formed between the phosphorus atom and an oxygen atom, that is, another 2 dollars $electrons are used, so that the 8 dollars $electron stability structure is reached around the oxygen atom. The number of electrons shared around the phosphorus atom at this time also satisfies the octet rule (by connecting with three oxygen atoms, including a double bond). The remaining 14 dollars - 2 = 12 $electrons are distributed in the form of lone pairs of electrons to the other two oxygen atoms, each oxygen atom has 6 dollars $lone pair electrons.
In this way, a reasonable Lewis structure of phosphite is constructed. From this structure, the chemical properties of phosphite can be further analyzed. For example, since there are two hydroxyl groups in the phosphite molecule, it can be partially ionized in aqueous solution, showing a certain acidity. Moreover, the oxidation state of phosphorus atoms in phosphite is $+ 3 $, which is in the intermediate valence state, which determines that it has both oxidation and reduction. Through in-depth analysis of the Lewis structure of phosphite, it is helpful for us to understand the chemical nature of phosphite and its behavior in chemical reactions more comprehensively.
