Draw the Lewis Structure for SiO3^2- with All Resonance Forms, State Its Formal Charge and Polarity, and Determine Its Molecular Geometry

To draw the Lewis structure for SiO₃^2-, follow these steps:

1. Count the total number of valence electrons: Silicon (Si) has 4 valence electrons, and each oxygen (O) has 6 valence electrons. Since there are three oxygen atoms and the molecule has a 2- charge, the total number of valence electrons is 4 + (3 × 6) + 2 = 24 electrons.
2. Place the least electronegative atom in the center: Silicon is less electronegative than oxygen, so it will be the central atom.
3. Connect the central atom to the surrounding atoms with single bonds: Draw single bonds between Si and each O atom. This uses 6 electrons (3 bonds × 2 electrons).
4. Distribute the remaining electrons: You have 18 electrons left. Place lone pairs on the oxygen atoms to satisfy the octet rule. Each oxygen will have 6 electrons in lone pairs, using up all 18 electrons.
5. Check for resonance structures: The double bond can be formed between Si and any of the three O atoms, leading to three resonance structures. In each resonance form, one oxygen will have a double bond with Si, and the other two will have single bonds.

Formal Charge Calculation:

• For Si: Formal Charge = 4 – 0 – 4 = 0
• For O with a double bond: Formal Charge = 6 – 4 – 2 = 0
• For O with a single bond: Formal Charge = 6 – 6 – 1 = -1

Polarity: The SiO₃^2- ion is polar due to the uneven distribution of electron density caused by the resonance structures and the presence of lone pairs on the oxygen atoms.

Molecular Geometry: The molecular geometry of SiO₃^2- is trigonal planar. The central Si atom is surrounded by three oxygen atoms, and the bond angles are approximately 120°.