What is the H₂SO₂ Lewis structure?

The Lewis structure of a molecule is a graphical representation that shows how the valence electrons are arranged among the atoms in the molecule. It helps to understand the molecular geometry, polarity, and reactivity of the compound. Here, we will discuss the Lewis structure of H₂SO₂ (Sulfurous acid).

Step 1: Determine the total number of valence electrons
The first step in drawing the Lewis structure for H₂SO₂ is to calculate the total number of valence electrons in the molecule. Hydrogen has 1 valence electron, sulfur has 6, and oxygen has 6. Since there are two hydrogen atoms and two oxygen atoms, the total number of valence electrons is (1*2) + 6 + (6*2) = 20.

Step 2: Identify the central atom
The central atom is usually the one that has the lowest electronegativity. In H₂SO₂, sulfur is the central atom.

Step 3: Draw a skeleton structure
Connect the central atom to the other atoms with single bonds. Each single bond uses 2 electrons, so after connecting sulfur to the two oxygens and two hydrogens, we have used 8 electrons, leaving us with 12.

Step 4: Distribute the remaining electrons
Start placing the remaining electrons as lone pairs on the outer atoms first (oxygen in this case). Each oxygen atom will get three lone pairs (6 electrons), using up all the remaining 12 electrons.

Step 5: Check the octet rule
The octet rule states that every atom (except hydrogen, which can only have 2) wants to have 8 electrons in its outer shell. The sulfur atom only has 4 electrons around it, so it does not fulfill the octet rule. To solve this, we can move one lone pair from each oxygen atom to form a double bond with the sulfur atom. Now, every atom fulfills the octet rule.

So, the Lewis structure of H₂SO₂ is a sulfur atom double-bonded to two oxygen atoms and single-bonded to two hydrogen atoms. Each oxygen atom also has two lone pairs, and the sulfur atom has no lone pairs.