Iyak gen chem

• Chemistry didn't make sense without the periodic table
• Dmitri Ivanovich Mendeleev


  Published a classification scheme for elements in 1869
• Mendeleev and Lothar Meyer published nearly identical classification schemes for elements known to date
• Henry Moseley


  His work in 1914 led to a revision of the periodic table by rearranging the elements by their atomic numbers
• Moseley concluded that the number of protons in an atom is its atomic number

  
• Valence electrons


  The electrons in the outer energy level of an atom that are transferred or shared when atoms bond together
• Types of elements

  • Metals
  • Non-metals
  • Metalloids
• Properties of metals


  • Good conductors of heat and electricity
  • Shiny
  • Ductile
  • Malleable
  • Reactive with water resulting in corrosion
• Properties of non-metals


  • Poor conductors of heat and electricity
  • Not ductile or malleable
  • Solid non-metals are brittle and break easily
  • Dull
  • Gases
• Properties of metalloids


  • Have properties of both metals and non-metals
  • Solids that can be shiny or dull
  • Conduct heat and electricity better than non-metals but not as well as metals
  • Ductile and malleable
• Families (groups)


  Columns of elements with similar but not identical properties
• Periods


  Horizontal rows of elements with properties that change greatly across the row
• Types of families


  • Hydrogen
  • Alkali metals
  • Alkaline earth metals
  • Transition metals
  • Boron family
  • Carbon family
  • Nitrogen family
  • Oxygen family
  • Halogen family
  • Noble gases
  • Rare earth elements
• Hydrogen


  Not a member of family IA, has one proton and one electron, only needs 2 electrons to fill its valence shell
• Alkali metals


  • Have a single electron in their outermost level, shiny, have the consistency of clay, easily cut with a knife, the most reactive metals, react violently with water, never found as free elements in nature
• Reactivity


  Elements that bond easily with other elements to make compounds
• What makes an element reactive

  An incomplete valence electron level, atoms want to have 8 electrons in their outermost energy level (rule of octet)

  
• Alkaline earth metals


  • Have two valence electrons, never found uncombined in nature
• Transition metals


  • Good conductors of heat and electricity, compounds are usually brightly colored, can lose electrons in their next-to-outermost level
• Boron family


  Atoms have 3 valence electrons
• Carbon family


  Atoms have 4 valence electrons, includes a non-metal (carbon), metalloids, and metals, carbon is the "basis of life"
• 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


  Elements have 7 valence electrons, the most active non-metals, never found free in nature, only need to gain 1 electron to fill their outermost energy level, react with alkali metals to form salts
• Noble gases


  • Colorless, extremely unreactive gases, have a full outermost energy level, called inert
• 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 (synthetic or man-made)
• Electron behavior in the periodic table

  • West (South) - Metals tend to give up electrons and form cations
  • Mid-plains - Metalloids will give up or accept electrons
  • East (North) - Non-metals tend to accept electrons and form anions
• Chemical bonding


  Happens when there is transfer or sharing of electrons
• Major types of chemical bonding

  • Ionic bonding - forms ionic compounds, transfer of electrons
  • Covalent bonding - forms molecules, sharing of electrons
• Metallic bonding


  Occurs between like atoms of a metal, valence electrons are mobile and move freely among all metal atoms, positive ions in a sea of electrons
• Metallic characteristics


  • High melting and boiling points, ductile, malleable, shiny, hard, good conductors of heat and electricity
• Ionic bonding


  Electrons are transferred between valence shells of atoms, ionic compounds are made of ions, always formed between metals and non-metals, electronegativity difference > 2.0

  
• Properties of ionic compounds


  • Hard solids at room temperature, high melting points, nonconductors of electricity in solid phase, good conductors in liquid phase or dissolved in water
• Covalent bonding


  Pairs of electrons are shared between non-metal atoms, electronegativity difference < 2.0, forms polyatomic ions

  
• Properties of molecular substances


  • Low melting and boiling points, relatively soft solids, nonconductors of electricity
• Types of covalent bonds

  • Single bonds - share 2 electrons
  • Double bonds - share 4 electrons
  • Triple bonds - share 6 electrons

  
• Molecule


  A neutral group of two or more non-metal atoms held together
• Covalent bond


  • Shared between non-metal atoms
  • Electronegativity difference < 2.0
  • Forms polyatomic ions

  
• Molecular substances


  • Low melting and boiling points
  • Relatively soft solids compared to ionic compounds
  • Nonconductors of electricity in any phase
• Drawing molecules using Lewis dot structures


  1. Symbol represents the kernel of the atom (nucleus and inner electrons)

  2. Dots represent valence electrons

  3. Atoms are trying to complete their outer shell

  4. Number of bonds they can make is the total number of electrons they need