Simple molecular substances

• What are simple molecular substances made up of?

  Molecules containing a few atoms joined together by covalent bonds
• What is the chemical formula for hydrogen gas?


  H₂
• Why do hydrogen atoms need one more electron?


  To complete the first shell
• What is the chemical formula for oxygen gas?

  O₂
• How many electrons do oxygen atoms need to complete their outer shell?


  Two more electrons
• What is the chemical formula for methane?


  CH₄
• How many outer electrons does carbon have?


  Four outer electrons
• How many covalent bonds can carbon form with hydrogen atoms?


  Four covalent bonds
• What is the chemical formula for ammonia?

  NH₃
• What type of bonds do oxygen atoms form in oxygen gas?


  Double covalent bonds
• What is the chemical formula for chlorine gas?


  Cl₂
• How many electrons do chlorine atoms need to complete their outer shell?


  One more electron
• What is the chemical formula for nitrogen gas?


  N₂
• How many electrons do nitrogen atoms need to complete their outer shell?


  Three more electrons
• What are simple molecular substances made up of?

  Molecules containing a few atoms joined together by covalent bonds
• What is the chemical formula for water?


  H₂O
• How does oxygen bond with hydrogen in water molecules?


  Oxygen shares a pair of electrons with two H atoms
• What is the chemical formula for hydrogen chloride?


  HCl
• What are some common examples of simple molecular substances?

  • Hydrogen (H₂)
  • Oxygen (O₂)
  • Methane (CH₄)
  • Chlorine (Cl₂)
  • Nitrogen (N₂)
  • Water (H₂O)
  • Hydrogen Chloride (HCl)
• How do chlorine atoms bond in chlorine gas?


  Two chlorine atoms share one pair of electrons
• How do nitrogen atoms bond in nitrogen gas?


  Two nitrogen atoms share three pairs of electrons
• How do hydrogen atoms achieve a full outer shell?


  By forming single covalent bonds with other hydrogen atoms or other elements
• What type of bond is formed between two oxygen atoms in O₂?


  A double covalent bond
• What are the properties of simple molecular substances?

  1. Contain covalent bonds with simple molecular structures.
  2. Strong covalent bonds within molecules, weak intermolecular forces.
  3. Low melting and boiling points due to weak intermolecular forces.
  4. Most are gases or liquids at room temperature.
  5. Larger molecules have stronger intermolecular forces, increasing melting and boiling points.
  6. Do not conduct electricity due to lack of free electrons or ions.
• What is required to melt or boil a simple molecular compound?

  Breaking weak intermolecular forces, not covalent bonds
• How many covalent bonds can carbon form in methane (CH₄)?


  Four covalent bonds
• Why do most molecular substances exist as gases or liquids at room temperature?


  Because they have low melting and boiling points
• What type of bond is formed between two chlorine atoms in Cl₂?


  A single covalent bond
• How does the size of molecules affect the strength of intermolecular forces?


  Larger molecules have stronger intermolecular forces
• Why don't molecular compounds conduct electricity?


  They aren't charged, so there are no free electrons or ions
• What are weak intermolecular forces?


  • Forces of attraction between molecules
  • Much weaker than covalent bonds
  • Responsible for the physical properties of molecular substances
• How do nitrogen atoms achieve a full outer shell in N₂?


  By sharing three pairs of electrons to form a triple bond
• How are the covalent bonds formed in water (H₂O)?


  Oxygen shares a pair of electrons with two hydrogen atoms
• What is the similarity between hydrogen chloride (HCl) and the other simple molecular substances?


  Both atoms need one more electron to complete their outer shells
• What are the properties of simple molecular substances?


  1. Usually have single molecular structures
  2. Atoms are held by strong covalent bonds; intermolecular forces are weak
  3. Low melting and boiling points due to weak intermolecular forces
  4. Most are gases or liquids at room temperature
  5. Larger molecules have stronger intermolecular forces, increasing melting and boiling points
  6. Do not conduct electricity due to lack of free electrons or ions
• Why do simple molecular substances have low melting and boiling points?


  Because only weak intermolecular forces need to be broken
• What state are most molecular substances in at room temperature?

  Gases or liquids
• How does the size of molecules affect the strength of intermolecular forces?


  Larger molecules have stronger intermolecular forces
• Why don’t molecular compounds conduct electricity?


  Because they aren’t charged and lack free electrons or ions
• What happens to intermolecular forces when a simple molecular substance melts or boils?


  Weak intermolecular forces are broken, not covalent bonds