chem chapter 3: bonding

• What can the three states of matter be represented in?

  The particle model
• What happens at the melting point of a solid?

  The solid changes to a liquid
• What is the boiling point of a liquid?

  The temperature at which it changes to a gas
• What does the particle model assume about the particles in a substance?

  They are spherical and solid with no forces between them
• How does the amount of energy needed to change the state of a substance depend on the particles?

  It depends on the forces between the particles
• What is a covalent bond?

  It is when electrons are shared between non-metal atoms
• What determines the number of electrons shared in a covalent bond?

  How many extra electrons an atom needs for a full outer shell
• What is a single bond in terms of electron sharing?

  Each atom shares one pair of electrons
• What is a double bond in terms of electron sharing?

  Each atom shares two pairs of electrons
• What happens to an atom when it gains or loses electrons?

  It becomes an ion with a charge
• What is the overall charge of a sodium atom (Na)?


  0
• What happens to a sodium atom when it loses an electron?

  It becomes a sodium ion (Na+) with a charge of 1+
• Why do solid ionic substances not conduct electricity?

  Because the ions are fixed in position
• When do ionic substances conduct electricity?

  When melted or dissolved in water
• Why do ionic substances have high melting points?

  Because the electrostatic forces between ions are strong
• What happens when metal atoms react with non-metal atoms?

  They transfer electrons to the non-metal atom
• What do metal atoms become when they lose electrons?

  Positive ions
• What do non-metal atoms become when they gain electrons?

  Negative ions
• What is ionic bonding?

  It is the attraction between positive and negative ions
• What is the structure of a giant ionic lattice?

  A regular structure of alternating positive and negative ions
• How is the formula of an ionic substance determined?

  From its bonding or lattice diagram
• What is a giant covalent structure?

  Many billions of atoms bonded together by strong covalent bonds
• What are small molecules made of?

  Only a few atoms with strong covalent bonds
• What are polymers?

  Many repeating units joined by covalent bonds
• Why do giant covalent substances have high melting points?

  It takes a lot of energy to break the strong covalent bonds
• Why do small molecules have low melting points?

  Only a small amount of energy is needed to break weak intermolecular forces
• Why do large molecules have higher melting and boiling points than small molecules?

  The intermolecular forces are stronger in large molecules
• Why do most covalent substances not conduct electricity?

  They do not have delocalised electrons or ions
• What is the structure of graphite?

  Each carbon atom is bonded to three others in hexagonal rings arranged in layers
• Why can graphite conduct electricity?

  The delocalised electrons can move through the graphite
• Why is graphite softer than diamond?

  The layers can slide over each other because they are not covalently bonded
• What is graphene?

  One layer of graphite
• What are two properties of graphene?

  Strong and conducts electricity
• What is a fullerene?

  A hollow cage of carbon atoms arranged as a sphere or a tube
• What is a nanotube?

  A hollow cylinder of carbon atoms
• What are two properties of nanotubes?

  High tensile strength and conduct electricity
• What are three uses of fullerenes?

  Lubricants, drug delivery, and high-tech electronics
• What is an ion?

  An atom that has lost or gained electrons
• Which kinds of elements form ionic bonds?

  Metals and non-metals
• What charges do ions from Group 1 form?

  1+