i. State THREE (3) properties of covalent compounds.
ii. Draw the Lewis structure for the molecule of ammonia (NH3).
iii. State the geometry of, and the bond angles in, the ammonia (NH3) molecule.
iv. PH3 has the same geometry as NH3, however, the bond angle in PH3 is less than that in NH3. Provide an explanation for this observation.
I) Low boiling points and melting points.
Poor conductors of heat and electricity.
iii) In the ammonia molecule, one of the electron pairs is a lone pair rather than a bonding pair. The molecular geometry of NH 3 is called trigonal pyramidal (see Figure 9). Recall that the bond angle in the tetrahedral CH 4 molecule is 109.5°.
iv) The bond angle in NH3 is larger than, in PH3 because the P−H bonds are longer and the lower electronegativity of P permits electron-density to be displaced towards hydrogen to a greater extent than in the case of NH3.