Simple molecular substances

• What is a covalent bond?

  A covalent bond is a shared pair of electrons.
• What results from covalent bonding?

  Covalent bonding results in the formation of molecules.
• What are the properties of simple molecular substances?

  They have low melting and boiling points, and do not conduct electricity.
• What is the smallest part of an element that can exist?

  An atom.
• How is a covalent bond formed between atoms?

  A covalent bond is formed when atoms share electrons to achieve a full outer shell of electrons.
• What type of elements usually form covalent bonds?

  Non-metals.
• How many electrons does each atom contribute to a shared pair in a covalent bond?

  Each atom contributes one electron to the shared pair of electrons.
• What is a molecule?

  A molecule is a collection of two or more atoms held together by chemical bonds.
• What is the difference between a molecule of the same element and a compound?

  A molecule of the same element consists of one type of atom, while a compound is formed by the chemical union of two or more elements.
• What is the typical size range of simple molecules?


  Simple molecules are typically around 0.1 nm or $10^{-10} m$ across.
• Why are individual atoms and molecules too small to see with a light microscope?

  They are too small to see even with the strongest light microscope.
• What type of microscope can produce images of atoms and simple molecules?

  Some electron microscopes can produce images of atoms and simple molecules.
• What is a covalent bond?

  A shared pair of electrons
• What results from covalent bonding?

  The formation of molecules
• What are the melting and boiling points of simple molecular substances like?

  They have low melting and boiling points
• Why do simple molecular substances not conduct electricity?

  They do not contain charged particles that can move
• What are the physical properties of simple molecular substances?

  • Low melting points
  • Low boiling points
  • Often liquids or gases at room temperature
• What is the definition of melting point?

  The temperature at which a solid changes into a liquid
• What is the definition of boiling point?

  The temperature at which a substance rapidly changes from a liquid to a gas
• What happens to energy during melting and boiling?

  Energy is transferred to overcome bonds or forces of attraction
• What is the relationship between energy needed and melting/boiling points?

  The more energy needed, the higher the melting or boiling point
• What are intermolecular forces?

  Weak attractive forces between molecules
• What happens to intermolecular forces when simple molecular substances melt or boil?

  Intermolecular forces are broken, not covalent bonds
• What is the melting point of water?

  0°C
• What is the boiling point of water?

  100°C
• Why can simple molecular substances not conduct electricity?

  They have no overall charge or free-moving charged particles
• What is a key fact about melting and boiling of simple molecular substances?

  Weak intermolecular forces are overcome, not strong covalent bonds
• What are the properties of simple molecular substances?

  • Low melting points
  • Low boiling points
  • Do not conduct electricity
  • Often liquids or gases at room temperature