Question

How does molecular structure relate to the properties that we can see?

Answer 1

Yes, molecular structures relate their properties.

1. Physical properties like solubility in water, M.P., dipole moment, B.P. etc and chemical properties depends on which type of functional group present in the molecule.

2. Which type of bond present in the molecule just example: Ionic bond

NaCl, AlCl3 and MgCl2

3. For ionic compounds they have high M.P. and have strong electrostatic interaction present between the ions.

4. They are generally soluble in water, good conductor in aq solution, non-directional.

5. But BaSO4, CaCO3 are not dissolved in water due to very high L.E.

6. Properties based on center atom and position of atom which placed in the periodic table.

Just examples:

7. I and II group metals always make ionic compound due to low ionization potential and their properties are same.

All hydroxide are bases, they show MOH (+1) and M(OH)2 +2 oxidation states.

8. All halogen make ionic as well as covalent compound like Chlorate, iodate they show oxidant.

8. Carbon group family makes covalent compound:

10. Alkanes, silanes and their derivatives alcohols, silicates they are highly polar and dissolves in water due to make hydrogen bonds with water.

11. If molecular structure is close packed and as increase the mass M.P. also increases in their homologous series.

But if branched the structure surface area will be lowered and decreased the B.P.

Iso butane has low B.P. than n-butane

12. Covalent compounds (Non-polar) not dissolved in water like all alkanes, alkenes due to lipophilic character.

But polar covalent make hydrogen bond with water and soluble ex: alcohols, acids.

13. If compound is symmetrical like BF3 Dipole moment will be zero and its D.M. observed zero means it is trigonal planar, but NH3 is pyramidal and shows polar character having some dipole moment and dissolves in water.

13. All molecules which have same functional group show similar chemical properties.

Once more example: Allotropes of C:

Diamond has three dimensional network structure therefore it becomes hard, high M.P. used as cutter,sp3 C, bad conductor of electricity.

But Graphite,allotropes of Carbon, it has layered hexagonal structure, sliding layered, having weak Van der Waals interaction, used as a lubricant, soft., sp2 C, good conductor of electricity.