Chem2

• Mendeleev and Lothar Meyer published nearly identical classification schemes for elements known to date


  1869
• The periodic table is based on the similarity of properties and reactivities exhibited by certain elements
• Moseley's work led to a revision of the periodic table by rearranging the elements by their atomic numbers


  1914
• Moseley concluded that the number of protons in an atom is its atomic number
• Elements


  • 90 naturally occurring elements
  • 28 created elements
• The elements, alone or in combinations, make up our bodies, our world, our sun, and in fact, the entire universe
• Valence electrons


  Electrons in the outer energy level of an atom
• Metals


  • Conductors of heat and electricity
  • Shiny, ductile, malleable
  • Reaction with water which may result in corrosion
• Non-Metals


  • Poor conductors
  • Not ductile nor malleable
  • Solid non-metals are brittle and can break easily
  • Dull
• Metalloids


  • Metal like
  • Solids that can be shiny or dull
  • Conducts heat and electricity but not as well as metals
  • Ductile and malleable
• Groups/Families


  Columns of elements with similar but not identical properties
• All elements in a family have the same number of valence electrons
• Hydrogen


  • Not a member of Family IA, in a class of its own
  • A gas at room temperature
  • Has one proton and one electron in its only energy level
  • Hydrogen only needs 2 electrons to fill up its valence shell
• Alkali Metals


  • Found in the first column of the periodic table
  • Atoms have a single electron in their outermost level
  • Shiny, have the consistency of clay, and are easily cut with a knife
• Reactivity


  Elements that bond easily with other elements to make compounds
• Reactivity


  An incomplete valence electron level. All atoms (except H) want to have 8 electrons in their very outermost energy level (Octet Rule)
• Alkaline Earth Metals


  • Never found uncombined
  • Have 2 valence electrons
• Transition Metals


  • Good conductors of heat and electricity
  • When combined, can give or provide heat and electricity
  • Bright colors
• Boron Family


  • Atoms have 3 valence electrons
• Carbon Family


  • Atoms have 4 valence electrons
  • Includes a non-metal (carbon), metalloids, and metals
  • Carbon is called the "basis of life"
  • Entire branch of chemistry devoted to carbon compounds called organic chemistry
• Nitrogen Family


  • Atoms have 5 valence electrons
  • Includes non-metals, metalloids, and metals
  • Tend to share electrons when they bond
• Oxygen Family


  • Atoms have 6 valence electrons
  • Most elements share electrons when forming compounds
  • Oxygen is the most abundant element in the earth's crust and extremely active
• Halogen Family


  • Halogens have 7 valence electrons
  • Most active non-metals
  • Never found free in nature
  • Halogen atoms only need to gain 1 electron to fill their outermost energy level
  • React with alkali metals to form salts
• Noble Gases


  • Colorless gases that are extremely unreactive
  • Inactive because their outermost energy level is full
  • Do not readily combine with other elements to form compounds
• Rare Earth Elements


  • Composed of the lanthanide and actinide series
  • One element of the lanthanide series and most of the elements in the actinide series are called trans-uranium, which means synthetic or man-made
• Electron Configuration


  Arrangements of electrons in an atom
• Aufbau's Principle


  Electrons fill orbitals starting from the lowest energy orbital, then proceed to fill each lower energy orbital, one electron at a time, before filling a higher energy level
• Pauli Exclusion Principle


  An atomic orbital can contain at most two electrons with opposite spins
• Hund's Rule


  When electrons occupy orbitals of equal energy, one electron enters each orbital until all degenerate orbitals contain one electron with parallel spins
• Atomic Radius


  • The distance between the nuclei of atoms (internuclear distance)
  • Decreases from left to right across a period as energy level remains the same and electrons are being added
• Ionic Radius


  • Metals readily lose electrons to form positive ions
  • Cations are smaller than the atoms from which they are formed
• Ionization Energy


  • The amount of energy a gaseous atom absorbs to remove an electron in its ground state
  • I1 is the first ionization energy, I2 is the second ionization energy
• Electron Affinity


  The amount of energy released when an electron is added to a gaseous atom
• Electronegativity


  The ability of an atom in a compound to attract electrons to itself
• Ionic Bonding


  • Electrons are transferred between valence shells of atoms
  • Ionic compounds are made of ions and called Salts or Crystals
  • Always formed between METALS and NON-METALS
  • Properties: hard solid at 22 oC, high mp, nonconductors in solid phase, good conductors in liquid phase or dissolved in water
• Covalent Bonding


  • Electrons are shared between atoms
  • Forms Molecules
  • Properties: low mp and bp, relatively soft solids, nonconductors of electricity
• Non-polar Covalent Bonds


  Electrons are shared equally between atoms of the same element
• Polar Covalent Bonds (Dipoles)


  Electrons are not shared equally between atoms of different elements
• Metallic Bonding


  • Occurs between like atoms of a metal in the free state
  • Valence electrons are mobile and move freely among all metal atoms
  • Positive ions in a sea of electrons
  • Properties: high mp, ductile, malleable, shiny, hard, good conductors of heat and electricity
• Lewis Dot Structure


  • Symbol represents the KERNEL of the atom (nucleus and inner electrons)
  • Dots represent valence electrons