Simpile molecular substances

• Simple Molecular Substances

  Substances made up of molecules containing atoms joined together by covalent bonds
• Hydrogen atoms

  • Have just one electron
  • Need one more electron to complete the first shell
• Hydrogen atoms forming bonds

  1. Share electrons with other hydrogen atoms or other elements

  2. To achieve a full outer shell
• Methane, CH4

  • Carbon has four outer electrons, which is half full
  • Can form four covalent bonds with hydrogen atoms to fill up the outer shell
• Ammonia, NH3

  • Nitrogen atoms need three electrons to complete their outer shell
  • They share these electrons by forming a triple bond
• Chlorine, Cl

  • Chlorine atoms need one electron to complete their outer shell
  • They can share one pair of electrons and form a covalent bond
• Nitrogen, N2

  • Nitrogen atoms need three electrons to complete their outer shell
  • They share these electrons by forming a triple bond
• Water, H2O

  • Oxygen shares a pair of electrons with two hydrogen atoms to form two single covalent bonds
• Hydrogen Chloride, HCl

  • Hydrogen and chlorine atoms only need one more electron to complete their outer shells
  • They form a covalent bond
• Simple Molecular Substances

  • Have small molecular structures
  • Atoms are held together by strong covalent bonds
  • Intermolecular forces between molecules are weak
• Simple Molecular Substances

  • Melt and boil at low temperatures as only weak intermolecular forces need to be broken
  • Most are gases or liquids at room temperature
  • As molecules get bigger, intermolecular forces increase, requiring more energy to break them
• Simple molecular substances don't conduct electricity because they aren't charged and have no free electrons or ions
• Oxygen, O2, is a gas at room temperature

  Because the intermolecular forces between oxygen molecules are weak
• Nitrogen, N2, doesn't conduct electricity

  Because it has no free electrons or ions