Draw the Lewis structure for ammonia,  NH3.     Determine from your diagram the shape and polarity of the covalent molecule.

1. Identify the central atom: The central atom is usually the one that can form the most bonds, which in this case is Nitrogen (N).

2. Count the total number of valence electrons: Nitrogen has 5 valence electrons and each Hydrogen atom has 1 valence electron. Since there are 3 Hydrogen atoms, the total number of valence electrons is 5 + 3*1 = 8.

3. Draw a skeleton structure: Place the central atom (N) in the center and draw single bonds to the Hydrogen atoms.

4. Distribute the remaining electrons: After forming single bonds with the Hydrogen atoms, Nitrogen has 2 valence electrons left. These are placed on the Nitrogen atom as a lone pair.

5. Check the octet rule: Each atom should have 8 electrons in its outer shell (2 for Hydrogen). In this case, Nitrogen has 8 (2 from each Hydrogen bond and 2 from the lone pair) and each Hydrogen has 2 (from the bond with Nitrogen), so the octet rule is satisfied.

The Lewis structure for NH3 (ammonia) is:

   H
   |
H--N--H
   :

The shape of the NH3 molecule is trigonal pyramidal. This is because there are three bonded atoms and one lone pair of electrons on the central Nitrogen atom.

The polarity of the NH3 molecule is polar. This is because the Nitrogen atom is more electronegative than the Hydrogen atoms, causing the bonded electrons to be more attracted to Nitrogen. This creates a region of partial negative charge near the Nitrogen atom and regions of partial positive charge near the Hydrogen atoms, resulting in a polar molecule.