The Lewis dot structure for silicon tetrabromide (SiBr4) illustrates how the valence electrons are arranged around the silicon atom and its bonding with bromine atoms.
To begin, silicon (Si) is the central atom because it can form four bonds. It has four valence electrons. Bromine (Br), on the other hand, is a halogen that has seven valence electrons and will form one bond. Since there are four bromine atoms, they will each share one pair of electrons with silicon.
1. **Count the total number of valence electrons**: Silicon has 4 valence electrons, and each bromine has 7, leading to a total of:
- 4 (from Si) + 4 × 7 (from 4 Br) = 4 + 28 = 32 valence electrons.
2. **Arrange the atoms**: Place the silicon atom in the center and surround it with the four bromine atoms.
3. **Draw bonds**: Connect each bromine atom to the silicon atom with a single line (representing a bonding pair of electrons). This uses up 8 electrons (2 for each bond).
4. **Distribute remaining electrons**: The remaining electrons (32 total – 8 used = 24 electrons) will fill the octets of the bromine atoms. Each bromine will have three lone pairs, totaling 6 electrons per bromine atom:
- 4 Br × 6 = 24 electrons completely fills the octets.
After completing these steps, the Lewis dot structure for SiBr4 can be represented as follows:
Br
:
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:---Si---:
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:
Br
Each bromine atom has 3 lone pairs and is single bonded to the silicon atom, which has no lone pairs. This structure best represents the molecular geometry of SiBr4 as tetrahedral, confirming that all atoms have achieved stable electron configurations.