Cham 3,4

• How are atoms and ions held together?

  By chemical bonds
• What is metallic bonding?

  Attraction between positive ions and delocalised electrons
• What is the definition of a covalent bond?

  A shared pair of electrons between atoms
• How does a covalent bond hold two atoms together?

  By attraction between nuclei and shared electrons
• Why do atoms form bonds?

  To achieve a stable electron arrangement
• What is the definition of a molecule?

  Two or more non-metal atoms joined by bonds
• What do bonding diagrams illustrate?

  How outer electrons form a covalent bond
• What is a diatomic molecule?

  A molecule containing only two atoms
• Name the elements that exist as diatomic molecules.

  H₂, O₂, N₂, F₂, Cl₂, Br₂, I₂
• What shapes can simple two-element compounds have?

  Linear and bent shapes
• What do perspective formulas show?

  Shapes of pyramidal and tetrahedral compounds
• What are the two structures of covalent substances?

  Covalent network and covalent molecular
• What type of element makes positive ions?

  Metals
• What type of element makes negative ions?

  Non-metals
• How are positive and negative ions formed?

  By losing or gaining electrons
• How does an ionic bond hold ions together?

  By attraction between positive and negative ions
• What is the arrangement of ions in an ionic compound?

  An ionic lattice
• What types of bonding are present in solids at 20°C?

  Metallic, ionic, covalent network
• What type of bonding is present in liquids and gases at 20°C?

  Covalent molecular
• Why are some covalent substances solid at 20°C?

  They have strong covalent networks requiring energy to break
• Why are other covalent substances liquids or gases at 20°C?

  They have weak forces that require little energy to break
• Why are ionic compounds solid at 20°C?

  Strong forces between oppositely charged ions
• What type of solvents can some covalent compounds dissolve in?

  Nonaqueous solvents
• What happens when an ionic compound dissolves in water?

  The lattice breaks and ions can move
• What is meant by an electric current?

  A flow of charged particles
• Why are metallic elements good conductors of electricity?

  They have delocalised electrons that move freely
• When do ionic compounds conduct electricity?

  When molten or in solution
• Why do ionic compounds conduct electricity when molten or dissolved?

  The ions are free to move
• How can it be proved that ions are charged particles?

  Through migration experiments showing ion movement
• What are the common elements and compounds of covalent network structures?

  • Elements: Silicon, Boron, Carbon (diamond and graphite)
  • Compounds: Silicon dioxide, Silicon carbide
• What are examples of covalent molecular substances?

  • Diatomic elements: H₂, O₂, N₂, F₂, Cl₂, Br₂, I₂
  • Compounds: Water, Carbon dioxide, Sugar
• What are the differences between covalent network and covalent molecular substances?

  • Covalent network: Strong bonds, high melting points, large structures
  • Covalent molecular: Weak forces, low melting points, small discrete molecules
• What determines the shape of a molecule?

  • The number of bonds in the molecule
• What is the role of delocalised electrons in metallic bonding?

  • They allow for electrical conductivity and malleability
• What happens to ionic compounds when they dissolve in water?

  • The ionic lattice breaks, allowing ions to move freely