To draw the Lewis structure for chlorate (ClO3–), we start by calculating the total number of valence electrons. Chlorine (Cl) has 7 valence electrons, and each oxygen (O) has 6 valence electrons. Since there are three oxygen atoms, that’s 3 x 6 = 18 electrons from oxygen. The overall charge of -1 contributes an additional electron. Thus, the total is:
- 7 (from Cl) + 18 (from 3 O) + 1 (additional electron) = 26 valence electrons.
Next, we place Cl in the center and surround it with the three O atoms. We will first connect the chlorine to each oxygen with a single bond, using 6 electrons (3 bonds x 2 electrons per bond). This leaves us with 20 electrons to account for.
To satisfy the octet rule for oxygen, we need to place lone pairs around the oxygen atoms. Initially, we can place 6 electrons (3 pairs) on each oxygen. However, two of the oxygens need to form double bonds with chlorine to keep the molecule stable and satisfy formal charge considerations. Therefore, we create two double bonds and one single bond with an oxygen. After adjusting, we have:
- 2 double bonds with 2 oxygen atoms
- 1 single bond with the third oxygen, which also carries a negative charge due to it being less than the 8 electrons.
Now, let’s explore the molecular geometry. The regions of electron density include the bonding pairs (double bonds and a single bond with the -1 charge). There are a total of three bonding pairs and one lone pair on the chlorine atom. This gives us a total of 4 regions of electron density.
Using VSEPR theory, we find that four regions of electron density around a central atom correspond to a tetrahedral electron geometry. The presence of one lone pair will cause the molecular geometry to be trigonal pyramidal.
In summary:
- Electron Geometry: Tetrahedral
- Molecular Geometry: Trigonal Pyramidal