Draw the Lewis diagram for each of the following compounds. Use Xs for the metal’s valence electrons and dots for the non-metal’s valence electrons. Then name the compound. a) The compound formed between aluminum and nitrogen: AlN b) The compound formed between sodium and phosphorus: Na3P c) The compound formed between silver and sulfur: Ag2S d) The compound formed between hydrogen and chlorine: HCl e) The compound formed between calcium and oxygen: CaO f) The compound formed between carbon and fluorine: CF4 g) The compound formed between hydrogen and nitrogen: HCN h) The compound formed between oxygen and fluorine: OF2
The Correct Answer and Explanation is:
Here are the Lewis diagrams and compound names for the given pairs. In each case, metals use Xs for their valence electrons and non-metals use dots.
a) AlN (Aluminum nitride)
Al: [Al] → X X X (3 valence electrons)
N: [·····] (5 valence electrons)
Al gives 3 electrons to N forming Al³⁺ and N³⁻
Diagram:Al³⁺ [···N···]³⁻
Name: Aluminum nitride
b) Na₃P (Sodium phosphide)
Each Na: [Na] → X
P: [·····]
Each Na donates 1 electron to P
Diagram:3Na⁺ [···P···]³⁻
Name: Sodium phosphide
c) Ag₂S (Silver sulfide)
Each Ag: [Ag] → X
S: [······]
Each Ag donates 1 electron to S
Diagram:2Ag⁺ [···S···]²⁻
Name: Silver sulfide
d) HCl (Hydrogen chloride)
H: X
Cl: [······]
H shares one electron with Cl
Diagram:X : Cl······
Name: Hydrogen chloride
e) CaO (Calcium oxide)
Ca: [Ca] → X X
O: [······]
Ca donates 2 electrons to O
Diagram:Ca²⁺ [···O···]²⁻
Name: Calcium oxide
f) CF₄ (Carbon tetrafluoride)
C: 4 valence electrons
F: [······]
C shares one electron with each of the four F atoms
Diagram:··F:C:F·· (and two more Fs in similar bonds)
Name: Carbon tetrafluoride
g) HCN (Hydrogen cyanide)
H: X
C: 4 valence electrons
N: [·····]
Triple bond forms between C and N; single bond between H and C
Diagram:X–C≡N··
Name: Hydrogen cyanide
h) OF₂ (Oxygen difluoride)
O: [······]
Each F: [······]
O shares one electron with each F
Diagram:··F–O–F··
Name: Oxygen difluoride
Explanation
Lewis diagrams are a way of representing the valence electrons of atoms in molecules and compounds. In these diagrams, we use Xs for the metal atoms’ electrons and dots for non-metal atoms. The diagrams help visualize how atoms achieve stable electron configurations by transferring or sharing electrons.
In ionic compounds such as AlN, Na₃P, Ag₂S, and CaO, metals lose electrons and become positively charged ions. Non-metals gain these electrons and become negatively charged. For example, aluminum has three valence electrons, which it gives to nitrogen that needs three electrons to complete its octet. This creates an ionic bond between Al³⁺ and N³⁻.
In covalent compounds such as HCl, CF₄, HCN, and OF₂, atoms share electrons to achieve full outer shells. In HCl, hydrogen shares one electron with chlorine, allowing both to have stable configurations. In CF₄, carbon shares its four electrons with four fluorine atoms, resulting in four single covalent bonds.
HCN is a special case with both single and triple covalent bonds. Hydrogen bonds once with carbon, and carbon forms a triple bond with nitrogen to fulfill the octet rule. This is an example of a molecule with multiple bond types.
OF₂ is also covalent, with oxygen sharing one electron with each fluorine atom. Oxygen still retains two lone pairs, giving it a bent molecular shape.
Understanding the type of bonding—ionic or covalent—is key to predicting the structure and properties of compounds. Lewis diagrams are a foundational tool for learning these principles in chemistry.
