1. Determine the central atom:
* Boron (B) is the least electronegative atom, so it will be the central atom.
2. Count the valence electrons:
* Sodium (Na) has 1 valence electron.
* Boron (B) has 3 valence electrons.
* Hydrogen (H) has 1 valence electron.
* Total valence electrons = 1 + 3 + (4 * 1) = 8
3. Draw the skeletal structure:
* Place the boron atom in the center.
* Connect the four hydrogen atoms to the boron atom.
4. Distribute the valence electrons:
* Each hydrogen atom needs 1 electron to complete its duet.
* Boron needs 8 electrons to complete its octet.
5. Check for formal charges:
* Sodium (Na) has a +1 charge.
* Borohydride (BH4-) has a -1 charge.
The Lewis dot structure for sodium borohydride (NaBH4) is:
```
H
|
H - B - H
|
H
Na+
```
Key points:
* The boron atom has 4 single bonds to the hydrogen atoms, completing its octet.
* Each hydrogen atom has a single bond, completing its duet.
* Sodium is shown as a separate ion with a +1 charge.
* The borohydride ion (BH4-) has a -1 charge.
Note: While this is a common representation, the actual structure of sodium borohydride is more complex involving ionic bonds and interactions. This Lewis structure is a simplified representation to illustrate the bonding and electron arrangement.
