Write the Lewis structure for each molecule. b. SiH₄

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1. Identify the total number of valence electrons in the molecule. Silicon (Si) has 4 valence electrons, and each hydrogen (H) has 1 valence electron. Since there are four hydrogens, the total number of valence electrons is 4 (from Si) + 4 (from 4 H) = 8 valence electrons.
2. Determine the central atom. In this case, silicon (Si) is less electronegative than hydrogen (H) and can form more bonds, so it will be the central atom.
3. Arrange the hydrogen atoms around the central silicon atom. Each hydrogen will form a single bond with silicon.
4. Distribute the valence electrons to form bonds. Use two electrons to form a single bond between each hydrogen and the silicon atom. This will use up all 8 valence electrons (4 bonds x 2 electrons per bond = 8 electrons).
5. Verify that each atom has a complete valence shell. Silicon will have 8 electrons around it (4 bonds), satisfying the octet rule, and each hydrogen will have 2 electrons (1 bond), satisfying the duet rule.

Key Concepts

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 in chemical reactions.

Valence Electrons

Valence electrons are the outermost electrons of an atom and are crucial in determining how an atom bonds with others. The number of valence electrons influences the molecule's reactivity and stability. For example, silicon (Si) has four valence electrons, which allows it to form four covalent bonds, as seen in the molecule SiH4.

Covalent Bonding

Covalent bonding occurs when two atoms share one or more pairs of electrons, allowing them to achieve a full outer electron shell. This type of bonding is common in molecules like SiH4, where silicon shares electrons with four hydrogen atoms. Understanding covalent bonding is key to predicting molecular shapes and properties.