Write the Lewis structure for each molecule. d. CH₄

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Identify the total number of valence electrons in the molecule. Carbon (C) has 4 valence electrons, and each hydrogen (H) has 1 valence electron. Since there are 4 hydrogen atoms, the total number of valence electrons is 4 (from C) + 4 (from 4 H) = 8 valence electrons.

Determine the central atom. In CH_4, carbon is the central atom because it is less electronegative than hydrogen and can form more bonds.

Arrange the hydrogen atoms around the central carbon atom. Each hydrogen atom will form a single bond with carbon.

Distribute the valence electrons to form bonds. Use a pair of electrons to form a single bond between the carbon atom and each hydrogen atom. This will use up all 8 valence electrons (4 bonds x 2 electrons per bond = 8 electrons).

Verify that each atom has a complete valence shell. Carbon should have 8 electrons around it (4 bonds), and each hydrogen should have 2 electrons (1 bond), satisfying the octet rule for carbon and the duet rule for hydrogen.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Lewis Structures

Lewis structures are diagrams that represent the bonding between atoms in a molecule and the lone pairs of electrons that may exist. They use dots to represent valence electrons and lines to represent bonds between atoms. Understanding how to draw Lewis structures is essential for visualizing molecular geometry and predicting the behavior of molecules.

Valence Electrons

Valence electrons are the outermost electrons of an atom and are crucial in determining how atoms bond with each other. The number of valence electrons influences the molecule's reactivity and stability. For example, carbon has four valence electrons, which allows it to form four bonds, as seen in methane (CH₄).

Molecular Geometry

Molecular geometry refers to the three-dimensional arrangement of atoms within a molecule. It is influenced by the number of bonds and lone pairs around the central atom, which can affect the molecule's physical and chemical properties. In the case of CH₄, the tetrahedral geometry arises from the four equivalent C-H bonds formed by carbon's four valence electrons.

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Textbook Question

Use the Born–Haber cycle and data from Appendix IIB and Table 10.3 to calculate the lattice energy of MgO. (ΔH_sub for magnesium is 137 kJ/mol; IE₁ and IE₂ for magnesium are 738 kJ/mol and 1450 kJ/mol, respectively; EA₁ and EA₂ for O are −141 kJ/mol and 744 kJ/mol, respectively.)