Draw a Lewis structure for each of the following ionic compounds. What chemical formula does Lewis theory predict?
a. sodium fluoride
b. calcium chloride
c. calcium oxide
d. aluminum chloride
The correct answer and explanation is :
Lewis Structure and Chemical Formula for Ionic Compounds
The Lewis theory of bonding involves the transfer of electrons between atoms to form stable ions. Ionic compounds are formed when electrons are transferred from one atom to another, creating positively charged cations and negatively charged anions. Let’s draw the Lewis structures for each of the following ionic compounds and explain the expected chemical formulas.
a. Sodium Fluoride (NaF)
- Lewis structure:
- Sodium (Na) has 1 valence electron in its outer shell, and fluorine (F) has 7 valence electrons.
- Sodium loses its 1 electron to become Na⁺, while fluorine gains that electron to become F⁻.
- The resulting ionic bond is formed by the electrostatic attraction between Na⁺ and F⁻.
- Chemical formula predicted by Lewis theory:
- Since Na donates 1 electron and F accepts 1 electron, the formula for sodium fluoride is NaF.
b. Calcium Chloride (CaCl₂)
- Lewis structure:
- Calcium (Ca) has 2 valence electrons, while chlorine (Cl) has 7 valence electrons.
- Calcium donates its 2 electrons to two chlorine atoms. Each chlorine atom gains 1 electron to become Cl⁻.
- The resulting ionic bonds are between Ca²⁺ and two Cl⁻ ions.
- Chemical formula predicted by Lewis theory:
- Calcium forms a Ca²⁺ ion, and each chlorine forms a Cl⁻ ion. Since two chloride ions are needed to balance the 2+ charge of calcium, the formula is CaCl₂.
c. Calcium Oxide (CaO)
- Lewis structure:
- Calcium (Ca) has 2 valence electrons, and oxygen (O) has 6 valence electrons.
- Calcium donates its 2 electrons to oxygen. Oxygen gains 2 electrons to form O²⁻.
- The ionic bond is between Ca²⁺ and O²⁻.
- Chemical formula predicted by Lewis theory:
- The formula for calcium oxide is CaO, as one Ca²⁺ ion and one O²⁻ ion are needed to balance the charges.
d. Aluminum Chloride (AlCl₃)
- Lewis structure:
- Aluminum (Al) has 3 valence electrons, and chlorine (Cl) has 7 valence electrons.
- Aluminum donates its 3 electrons to 3 chlorine atoms. Each chlorine atom gains 1 electron to become Cl⁻.
- The ionic bonds are formed between Al³⁺ and 3 Cl⁻ ions.
- Chemical formula predicted by Lewis theory:
- The formula for aluminum chloride is AlCl₃, as one Al³⁺ ion is paired with three Cl⁻ ions to balance the charges.
Conclusion
The Lewis theory of bonding predicts the following chemical formulas for the given ionic compounds:
- Sodium fluoride: NaF
- Calcium chloride: CaCl₂
- Calcium oxide: CaO
- Aluminum chloride: AlCl₃
These formulas reflect the electron transfer and resulting ionic charges based on the number of valence electrons in each atom.
