chem paper 1

• Element


  The smallest part of an element that can exist and still be that element
• There are about a hundred different elements and they are shown in the periodic table
• Compound


  Formed when elements combine together in chemical reactions, contains two or more elements chemically combined in fixed proportions
• Naming compounds from their formula

  1. Take the name of the metal and leave it as is

  2. Take the first syllable of the nonmetal and add 'ide'

  3. If there is oxygen, take the first syllable of the nonmetal and add 'ate'
• Mixture

  Two or more elements or compounds that are not chemically combined together, they are not bonded
• Physical separation processes

  • Filtration
  • Crystallization
  • Simple distillation
  • Fractional distillation
  • Chromatography
• Fractional distillation


  • Separates liquids according to their boiling point
  • Develops a temperature gradient in the fractionating column
• Chromatography

  Separates mixtures based on the solubility of the components in the mobile phase (solvent)
• Atom

  Consists of protons (positive particles in the nucleus), neutrons (neutral particles in the nucleus), and electrons (negative particles orbiting the nucleus)
• The average size of an atom is about 0.1 nanometers, but the nucleus is only one ten-thousandth of the diameter of the atom
• The relative mass of the electron is very small
• Isotopes

  Atoms of the same element that have different numbers of neutrons
• Calculating the relative atomic mass of a sample with different isotopes

  1. Find the percentage of each isotope

  2. Multiply the percentage by the mass of each isotope

  3. Add the results together
• Atomic models

  • Dalton model: atoms are indivisible spheres
  • Thomson model: atoms have electrons embedded in a positive charge
  • Rutherford model: atoms have a tiny dense nucleus surrounded by electrons
  • Bohr model: electrons orbit the nucleus in distinct shells
  • Modern model: nucleus contains protons and neutrons
• Periodic table

  • Elements are arranged in order of atomic number (number of protons)
  • Elements with similar properties are in vertical groups
  • Originally arranged by atomic weight, leading to some issues
• Groups in the periodic table

  • Group 1: one electron in outer shell
  • Group 2: two electrons in outer shell
  • Group 7: seven electrons in outer shell
  • Group 0: full outer shell, very unreactive
• Electrons in outer shell


  Determines how an element reacts with other elements
• Initially, elements were arranged according to their atomic weight, which led to some problems
• Dmitri Mendeleev left gaps in the periodic table and made predictions about undiscovered elements, which turned out to be correct
• Metals

  Elements that will react to form positive ions
• Nonmetals


  Elements that will react but won't form positive ions
• Metals

  • Malleable
  • Conductive
  • Have high melting points
• Group 1 (Alkali metals)


  Highly reactive metals that react with water to produce hydrogen gas and a metal hydroxide
• Group 7 (Halogens)


  Reactive elements that exist as diatomic molecules and can displace elements lower in the group
• Group 0 (Noble gases)


  Stable elements with full outer shells, with boiling points increasing down the group
• Metallic bonding involves regular rows of positive ions surrounded by a sea of delocalized electrons
• Ionic bonding involves the transfer of electrons from a metal to a nonmetal, forming a giant ionic lattice
• Covalent bonding involves the sharing of electron pairs between nonmetal atoms, forming either small molecules or giant covalent structures
• Polymers


  Long chains of repeating monomer units held together by covalent bonds, with weak intermolecular forces between chains
• Giant covalent structures are made up of thousands of atoms held together by strong covalent bonds
• Polymers


  Very long chains of repeating units called monomers, held together by strong covalent bonds
• Monomers

  Repeating units that make up polymers, held together by strong covalent bonds
• Intermolecular forces


  Weak forces between polymer chains, not as strong as covalent or ionic bonds
• Giant covalent structures

  • Diamond
  • Graphite
  • Graphene
  • Fullerenes
  • Silicon dioxide
• Diamond


  • Every carbon atom makes four strong covalent bonds
  • Incredibly hard
  • Does not conduct electricity
• Graphite

  • Every carbon atom makes three bonds, leaving one electron delocalized
  • Sheets held together by weak intermolecular forces, can slide over each other
  • Soft and slippery, useful as a lubricant
• Graphene

  • Single layer of graphite, can conduct electricity
• Fullerenes


  • Nanoparticles made of carbon atoms, form tubes and balls
• Silicon dioxide

  • Every silicon atom joined to four oxygen atoms by strong covalent bonds
  • High melting point, does not conduct electricity
• Relative atomic mass

  Mass of an element compared to 1/12 the mass of carbon-12