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
• Fixed proportions


  The same ratio of elements, shown by the formula
• Naming compounds from formula

  1. Take name of metal as is

  2. Take first syllable of nonmetal

  3. Add 'ide' for ionic compounds

  4. Add 'ate' if oxygen is present
• Mixture


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


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


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


  Separates mixtures based on the solubility of components in the mobile and stationary phases
• Atom


  Consists of protons (positive) in the nucleus, neutrons (neutral) in the nucleus, and electrons (negative) in shells around the nucleus
• Average size of an atom is about 0.1 nanometres, but the nucleus is only one ten-thousandth of the diameter of the atom
• Electrons have a very small but non-zero mass, they do not have a mass of zero
• Isotopes


  Atoms of the same element with different numbers of neutrons
• Calculating relative atomic mass from isotope abundances

  1. Multiply abundance by mass for each isotope

  2. 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 in distinct shells
  • Modern model - nucleus has protons and neutrons
• Periodic table


  • Elements arranged in order of atomic number (protons)
  • Elements with similar properties are in the same group (column)
  • Properties repeat periodically (rows)
• The periodic table was originally arranged by atomic weight, which had some issues, before being rearranged by atomic number
• Electrons in outer shell


  Determines how an element reacts with other elements
• The periodic table hasn't always been laid out like this
• 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
• Groups in the periodic table

  • Group 1 (alkali metals)
  • Group 7 (halogens)
  • Group 0 (noble gases)
• Alkali metals


  Very reactive, float on water, produce hydrogen gas, and can produce a lilac flame
• Halogens


  Group 7 elements, consist of molecules made of pairs of atoms, and become more reactive as you go up the group
• Noble gases


  Group 0 elements, have a full outer shell, and have boiling points that increase as you go down the group
• The next unit is about chemical bonds: metallic, ionic, and covalent
• Metallic bonding


  Positive ions in a sea of delocalized electrons, which makes metals malleable and conductive
• Ionic bonding


  Occurs between a metal and a nonmetal, involves the transfer of electrons, and forms a giant ionic lattice
• Covalent bonding


  Occurs between pairs of nonmetal atoms, where they share one or more pairs of electrons
• Types of covalent substances

  • Small covalent molecules
  • Giant covalent structures
• Polymers


  Very long chains of repeating units (monomers) held together by strong covalent bonds
• 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 4 strong covalent bonds
  • Doesn't have delocalized electrons or ions, so can't conduct electricity