The Lewis dot structure for selenium trioxide (SeO3) can be drawn by following these steps:
- Count the total number of valence electrons: Selenium has 6 valence electrons and each oxygen has 6 valence electrons. Therefore, SeO3 has a total of 6 + (3 x 6) = 24 valence electrons.
- Place the selenium atom in the center and arrange the three oxygen atoms around it.
- Use single bonds to connect Se to each O. This uses 6 electrons, leaving 18 electrons remaining.
- Distribute the remaining electrons to satisfy the octet rule for the oxygen atoms. Each oxygen will receive 6 electrons to complete its octet, using 18 electrons in the process.
- Next, check the central atom (Se). It currently holds 6 electrons (one from each bond). To satisfy the octet rule and complete the structure, we can form double bonds between Se and each O, sharing additional pairs of electrons.
After drawing the Lewis structure, we can answer the following questions:
a) How many electron domains are around the central atom?
There are three double bonds with oxygen atoms around the central selenium atom. Therefore, there are 3 electron domains.
b) What is the electron domain geometry?
The electron domain geometry for three electron domains is trigonal planar.
c) How many lone pairs are around the central atom?
In the case of SeO3, there are 0 lone pairs on the central selenium atom.
d) What is the molecular geometry?
Since there are no lone pairs affecting the shape, the molecular geometry of SeO3 is also trigonal planar.