Bonding, Structure and the Properties of Matter

• What is ionic bonding?

  Ionic bonding is the electrostatic force between positive and negative ions.
• How are ionic compounds held together?

  • They are held together in giant substances called lattices
  • It's a regular structure that extends in all directions in a substance
  • Electrostatic attraction between positive and negative ions holds the structure together
• What is covalent bonding?

  Covalent Bonding is a shared pair of electrons between Atoms.
• Describe the structure and properties of simple molecular covalent substances

  • Do not conduct electricity (no ions)
  • Small molecules
  • Weak intermolecular forces
  • Low boiling points
• How do intermolecular forces change as the mass/size of an atom increases?

  • They increase.
  • This causes the melting and boiling points to increase as more energy is required to break these bonds.
• What are polymers?

  Polymers are very large molecules with atoms linked together with covalent bonds.
• what is a Thermosoftening polymer?

  A polymer that softens when heated and hardens when cooled. Strong intermolecular forces hold the polymer together.
• Ionic bonding is the electrostatic attraction between positive and negative ions
• Ionic compounds are held together in a giant lattice structure that extends in all directions
• Properties of ionic substances:

  • High melting and boiling point
  • Do not conduct electricity when solid
  • Conduct when molten or dissolved in water
• Examples of positive ions: Na+, Mg2+, Al3+, Ca2+, Rb+

  Examples of negative ions (anions): Cl−, Br−, SO42−, NO3−, OH−

  Important to note that ionic compounds are electrically neutral
• Ionic compounds are formed through the reaction of a metal with a non-metal, involving electron transfer. In the case of MgO, Mg becomes Mg2+ and O becomes O2− (oxide)
• Covalent bond is a shared pair of electrons between two atoms
• Simple molecular covalent substances:

  • Do not conduct electricity
  • Consist of small molecules
  • Have weak intermolecular forces, leading to low melting and boiling points
• Intermolecular forces increase as the mass/size of the molecule increases, resulting in higher melting/boiling points
• Polymers are large molecules with covalent bonds. Thermosoftening polymers melt/soften when heated due to no bonds between polymer chains
• Giant covalent substances are solids with atoms covalently bonded in a giant lattice. Examples include diamond, graphite, and silicon dioxide
• Allotropes of carbon:

  • Diamond: very hard, high melting point, does not conduct
  • Graphite: layers of hexagonal rings, high melting point, conducts electricity
  • Fullerenes: hollow shaped molecules, nanotubes, graphene
• Metallic bonding is the attraction between delocalised electrons and metal ions
• Properties of metals:

  • High melting/boiling points
  • Good conductors of heat and electricity
  • Malleable and soft
• Alloys are mixtures of metals with other elements, making them harder than pure metals due to different sizes of atoms distorting layers
• The amount of energy needed to change state depends on the strength of forces between particles, type of bonding, and structure of the substance
• A pure substance will melt or boil at a fixed temperature, while a mixture will melt over a range of temperatures
• The three states of matter are solid, liquid, and gas
• Nanoscience studies particles that are 1-100nm in size
• Uses of nanoparticles include in medicine, electronics, deodorants, and sun creams for better skin coverage and protection against cell damage
• Fine particles (soot) have a diameter of 100-2500 nm, while coarse particles (dust) have a diameter of 2500-10^5 nm
• Nanoparticles have different properties due to their high surface area to volume ratio