5) Simple Molecular Substances:

What are Simple Molecular Substances?

Simple molecular substances are made up of molecules containing a few atoms joined together by covalent bonds. These substances typically have simple molecular structures.

Examples of Simple Molecular Substances

1. Chlorine (Cl₂):

   • Each chlorine atom needs one more electron to complete its outer shell.

   • Two chlorine atoms share a pair of electrons, forming a single covalent bond.

2. Hydrogen (H₂):

   • Hydrogen atoms have one electron and need one more to complete their first shell.

   • They form single covalent bonds, either with other hydrogen atoms or other elements.

3. Oxygen (O₂):

   • Oxygen atoms need two more electrons to fill their outer shell.

   • Two oxygen atoms share two pairs of electrons, creating a double covalent bond.

4. Nitrogen (N₂):

   • Nitrogen atoms need three more electrons to fill their outer shell.

   • Two nitrogen atoms share three pairs of electrons, forming a triple covalent bond.

5. Water (H₂O):

   • Oxygen shares a pair of electrons with two hydrogen atoms, forming two single covalent bonds.

6. Methane (CH₄):

   • Carbon has four outer electrons and can form four covalent bonds with hydrogen atoms to fill its outer shell.

7. Hydrogen Chloride (HCl):

   • Hydrogen and chlorine each need one more electron to complete their outer shells.

   • They share a pair of electrons to form a single covalent bond.

Properties of Simple Molecular Substances

• Weak Intermolecular Forces:

  • Atoms within molecules are held together by strong covalent bonds.

  • However, the forces of attraction between molecules are weak.

• Low Melting and Boiling Points:

  • To melt or boil a simple molecular compound, only the weak intermolecular forces need to be broken, not the covalent bonds.

  • This results in low melting and boiling points, as the molecules are easily separated.

• States at Room Temperature:

  • Most simple molecular substances are gases or liquids at room temperature.

• Increasing Size and Intermolecular Forces:

  • As molecules get bigger, the strength of the intermolecular forces increases, requiring more energy to break them.

  • This leads to higher melting and boiling points.

• Electrical Conductivity:

  • Molecular compounds do not conduct electricity because they aren't charged — they have no free electrons or ions.