Decide whether the molecules represented by the following formulas are polar or nonpolar. (You may need to draw Lewis structures and geometric sketches to do so.)
1. OF₂
2. CH₂Cl₂
3. HCN
4. SO₂
5. CH₄
Answer (2)
The molecules can be categorized as follows: OF₂, CH₂Cl₂, HCN, and SO₂ are polar, while CH₄ is nonpolar. This determination is based on their molecular geometry and the polarity of their bonds. Understanding the arrangement of atoms and the distribution of charge is key to identifying polarity.
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To determine whether a molecule is polar or nonpolar, we need to consider its shape and the difference in electronegativity between the atoms, which causes dipole moments. We can break it down for each molecule given:
OF₂
Lewis Structure and Shape: OF₂'s Lewis structure shows that it has two fluorine atoms bonded to one oxygen atom with two lone pairs on oxygen. It takes a bent shape, similar to H₂O.
Polarity: Oxygen and fluorine have different electronegativities, and because of the bent shape, the dipoles do not cancel out, making OF₂ a polar molecule.
CH₂Cl₂
Lewis Structure and Shape: CH₂Cl₂ has a tetrahedral shape with two hydrogen atoms and two chlorine atoms bonded to carbon.
Polarity: Chlorine is more electronegative than carbon and hydrogen, creating polar bonds. Due to the tetrahedral arrangement and the difference in electronegativity, the dipoles do not cancel out. Thus, CH₂Cl₂ is a polar molecule.
HCN
Lewis Structure and Shape: HCN is a linear molecule with hydrogen, carbon, and nitrogen bonded in that order. Nitrogen is more electronegative than carbon and hydrogen.
Polarity: Due to the linear shape and significant electronegativity difference across the molecule, the dipole moments do not cancel, making HCN polar.
SO₂
Lewis Structure and Shape: SO₂ has a bent shape with sulfur bonded to two oxygen atoms, and there’s a lone pair on sulfur, similar to the arrangement in water.
Polarity: The difference in electronegativity between sulfur and oxygen creates dipoles, and the bent shape means these dipoles do not cancel, making SO₂ polar.
CH₄
Lewis Structure and Shape: CH₄ is a tetrahedral molecule with four hydrogen atoms symmetrically surrounding a central carbon.
Polarity: The C-H bonds are considered to have small electronegativity differences, and due to the symmetry of the tetrahedral shape, the dipole moments cancel out. Thus, CH₄ is nonpolar.
