C: bonding: chemical bonds

• What are compounds?


  Substances in which 2 or more elements are chemically combined
• What are the three types of strong chemical bonds?

  Ionic, covalent, and metallic
• What characterizes ionic bonds?

  Particles are oppositely charged ions
• In what type of compounds do ionic bonds occur?

  In compounds formed from metals combined with non-metals
• What defines covalent bonds?

  Particles are atoms which share pairs of electrons
• Where do covalent bonds typically occur?

  In most non-metallic elements and in compounds of non-metals
• What characterizes metallic bonds?


  Particles are atoms which share delocalised electrons

  
• In what types of materials do metallic bonds occur?

  In metallic elements and alloys

  
• What happens to electrons during ionic bonding?

  Electrons in the outer shell of the metal atom are transferred

  
• What occurs to metal atoms during ionic bonding?

  Metal atoms lose electrons to become positively charged ions
• What happens to non-metal atoms during ionic bonding?

  Non-metal atoms gain electrons to become negatively charged ions

  
• What is an ion?


  An atom that has lost or gained electron(s)
• Which groups of elements produce ions in ionic bonding?

  Metals in Groups 1 and 2 and non-metals in Groups 6 and 7
• What electronic structure do ions produced by metals and non-metals achieve?

  They have the same electronic structure as a noble gas (Group 0 element)

  
• How can electron transfer during the formation of an ionic compound be represented?

  By a dot and cross diagram
• What is the structure of ionic compounds?

  A giant structure of ions
• How are ionic compounds held together?

  By strong electrostatic forces of attraction between oppositely charged ions
• Why do the forces in ionic compounds act in every direction?

  Because the structure is in 3D
• Give an example of an ionic compound.

  Sodium chloride (salt)
• What is covalent bonding?


  When atoms share one or more pairs of electrons
• Name some small molecules that have strong covalent bonds.

  HCl, H2, O2, Cl2, NH3, CH4
• What are polymers?


  Large covalently bonded molecules
• What are giant covalent structures?

  Structures that consist of many atoms covalently bonded in a lattice structure
• Give examples of giant covalent structures.

  Diamond, silicon dioxide

  
• How can covalent substances be represented in diagrams?

  Using dot and cross, repeat units for polymers, ball and stick, and two- and three-dimensional diagrams

  
• What is the arrangement of atoms in metallic bonding?

  Positive ions and delocalised electrons arranged in a regular pattern

  
• What is the delocalised electron system in metallic bonding?


  The electrons ‘lost’ from the atoms to form positive ions

  
• What is the significance of delocalised electrons in metallic bonding?

  They are free to move through the structure, making metallic bonds strong

  
• What are the key characteristics of ionic, covalent, and metallic bonding?

  • Ionic bonding: Oppositely charged ions, occurs between metals and non-metals
  • Covalent bonding: Atoms share pairs of electrons, occurs in non-metals
  • Metallic bonding: Positive ions and delocalised electrons, occurs in metals and alloys

  
• What are the properties of ionic compounds?


  • Giant structure of ions
  • Strong electrostatic forces of attraction
  • 3D structure with forces acting in all directions
• What are the properties of covalent compounds?

  • Strong covalent bonds within small molecules
  • Can form polymers and giant covalent structures
  • Represented in various diagram forms
• What are the properties of metallic compounds?

  • Regular arrangement of positive ions and delocalised electrons
  • Delocalised electrons contribute to strength and conductivity