Docstoc

Ch.-5-Notes-Periodic-Table

Document Sample
Ch.-5-Notes-Periodic-Table Powered By Docstoc
					 The periodic table is
  the most useful tool
  in chemistry.
 You get to use it on
  quizzes and tests!
 It organizes lots of
  information about all
  the known elements.
 …was a mess!!!
 No organization of
  elements.
 Imagine going to a
  grocery store with no
  organization!!
 Difficult to find
  information.
 Chemistry didn’t make
  sense.
 Previous attempts to organize known elements failed
  to work for all known elements at the time

 Russian Chemist and teacher, Dmitri Mendeleev,
  discovered a way

 Found a way to approach the problem when playing
  his favorite card game, a version of solitaire
  (organization was the key)
 Solitaire…??????
  HOW HIS WORKED…
 Put elements in rows by increasing atomic weight.
 Elements with similar properties were in the same
  column.
 Put elements in columns by the way they reacted.
 Periodic Table: an arrangement of elements in
 columns, based on a set of properties that repeat from
 row to row
 Table was not complete, not all elements had yet been
    discovered
   He left gaps/spaces in his table for those elements
   He was NOT the first to organize the elements in the
    form of a table
   He was the FIRST to offer good explanations for how
    the properties of an element were related to its
    location in his table
   He used the gaps in his tables to predict properties of
    undiscovered elements
   Other scientists used the predictions to help in their
    search for undiscovered elements
 The close match between Mendeleev’s predictions
  and the actual properties of new elements showed
  how useful his periodic table could be
 With the periodic table, chemists could do more
  than predict the properties of new elements – they
  could explain the chemical behavior of different
  groups of elements!!!
 Mendeleev wasn’t too far off.
 Now the elements are put in rows by increasing

 ATOMIC NUMBER!!
 The horizontal rows are called periods and are labeled
  from 1 to 7.
 The vertical columns are called groups are labeled
  from 1 to 18.
 Period: A row in a periodic table of elements (left to
  right)
 To understand the structure of the table, think what
  happens as the atomic number increases:
   Reminder: Atomic Number = Number of Protons
 First energy level has ONLY 1 orbital
   The 1 e- in a hydrogen atom and 2 e- in a helium atom
    can fit in this orbital (first energy level)
   This is why H and He are in Period 1
 Lithium, 1st element in Period 2, has one of its the
 three electrons in the second energy level
   This is why lithium is the first element in Period 2
 Sodium, 1st element in Period 3, has one e- in its third
  energy level
 Potassium, 1st element in Period 4, has 1 e- in its
  fourth energy level
 This pattern applies to ALL the elements in the 1st
  column on the table
 Columns are also grouped
  into families (or groups).
 Families may be one
  column, or several
  columns put together.
 Families have names (Just
  like your family has a
  common last name.)
 Group: A column in a periodic table of elements
 Properties of elements repeat in a predictable
 way when atomic numbers are used to arrange
 elements into groups
 Periodic Law: the pattern of repeating properties
  displayed by elements in the periodic table
 Elements within a group have similar properties:
   Similar e- configurations (see example above – first
    column of the table)
   Electron configuration determines an elements
    chemical properties
 Atomic mass is a value that depends on the
 distribution of an element’s isotopes in nature and
 the masses of those isotopes.
 Mass of an atom in grams is EXTREMELY small
 Scientists came up with an easier way to talk about
 mass
   Chose one isotope to serve as a standard
   Scientists assigned 12 atomic mass units (amu’s) to the
    carbon-12 atom (which has 6P and 6N)


 Atomic Mass Unit (amu): 1/12 the mass of a
 carbon-12 atom
 Chlorine has an atomic number of 17 and an
  atomic mass of 35.453 atomic mass units
 Where does the number 35.453 come from???
   There are two natural isotopes of Chlorine:
      Chlorine-35 which has 17 protons and 18 neutrons
      Chlorine-37 which has 17 protons and 20 neutrons
 Atomic masses come from an average of the
  isotopes for a given element that exist in nature
 The value for atomic mass is known as a “weighted
  average”

   Cl-35 occurs 3 times as often as Cl-37


   Take an average of those numbers:

                   (3 × 35) + (1 × 37)
                   -----------------------------   = 35.453
                                4
 Elements are classified as metals, nonmetals,
 and metalloids.
 Metals: elements that are good conductors of electric
  current and heat.
 Properties of Metals:
   Except for mercury, metals are solid at room
    temperature
   Most metals are malleable
   Many metals are ductile (can be drawn into thin wires)
   Some metals are extremely reactive* (page 135, figure 10)
      *Meaning they easily combine chemically with other
      elements
 Transition Metals: metals in groups 3-12, form a
 bridge between the elements on the left and right
 sides of the tables.
   Examples: copper and silver
   Some of the first elements discovered
   Ability to form compounds with distinctive colors
    (page 137  production of colored glass)
   Includes the lanthanide and actinide series (at the
    bottom of the table)
 Nonmetals: elements that are poor conductors of
 heat and electric current
   Properties opposite those of metals
     Low boiling points
     Most are gases at room temperature
     Nonmetals that are solid at room temperature
      tend to be brittle (will shatter)
     Some very reactive, some not at all, some fall
      somewhere in between
     Fluorine (in Group 17) is the most reactive
      nonmetal (found in toothpaste)
 Metalloids: elements with properties that fall
 between those of metals and nonmetals
   Ability to conduct electric current varies with
    temperature
   Pure silicon (Si) and germanium (Ge) are good
    insulators at low temperatures and good conductors
    at high temps.
 Across a period from left to right, the elements
 become less metallic and more nonmetallic in their
 properties
   Most reactive metals on left side
   Most reactive nonmetals on the right side (in Group 17)
   Period 3 elements (left to right) provide an example of
    this (page 138, Figure 13)
 Why is hydrogen (H)
  on the left side of the
  table with the active
  metals?
 Hydrogen’s location is
  related to its electron
  configuration, not its
  properties!!!
 Wonder why there are 2 numbering schemes on the
 periodic table?
   When the ‘A’ groups are numbered 1-8, they provide a
    reminder about the electron configurations of the
    elements in those groups
   The number of an ‘A’ group matches the number of
    valance electrons in an electron configuration for an
    element in that group
 Valence Electron: an electron that is in the highest
  occupied energy level of an atom
   Valence electrons play a key role in chemical reactions
   Properties vary across a period because the number of
    valence electrons increases from left to right
 Elements in a group have similar properties because
  they have the same number of valence electron
 Hydrogen is on far left of table because it has one
  valence electron, just like the rest of the elements in
  that column
 Hydrogen belongs to a
    family of its own.
   Hydrogen is a diatomic,
    reactive gas.
   Hydrogen was involved
    in the explosion of the
    Hindenberg.
   http://www.youtube.com
    /watch?v=F54rqDh2mW
    A
   Hydrogen is promising as
    an alternative fuel source
    for automobiles.
 1st column on the periodic table (Group 1
  /1A) not including hydrogen.
 Very reactive metals, always combined
  with something else in nature (like in
  salt).
 Single valence electron
 Soft enough to cut with a butter knife.
 The reactivity of alkali metals increases from the
  top of Group 1A to the bottom
 Lithium (Li) down through Francium (Fr)


 http://www.youtube.com/watch?v=m55kgyApYrY
 Group 2 / 2A on the periodic table.
 Reactive metals that are always
  combined with nonmetals in
  nature.
 Several of these elements are
  important mineral nutrients (such
  as Mg and Ca).
 2 valence electrons
 Harder than metals in Group 1A
 Higher melting point than Group 1A
 Differences in reactivity among the alkaline earth
 metals are shown by the ways they react with water
   Calcium, strontium, and barium react easily with
    cold water
   Magnesium reacts with hot water
   No change with beryllium and water
 Elements in groups 3-
  12
 Less reactive, harder
  metals.
 Includes metals used
  in jewelry and
  construction.
 Most are hard and
  shiny.
 Elements in group 13 (3A)
 Aluminum:
   Metal was once rare and expensive,
    not a “disposable metal.”
   Most abundant metal in Earth’s
    crust
   Less reactive than sodium and
    magnesium
   strong, lightweight, malleable, and
    good conductor of electric current
 3 valence electrons
 Boron is used in
 glassware like flasks
 because it doesn’t shatter
 when it undergoes a rapid
 temperature change
 Elements in group 14 (4A)
 Group 4A contains one nonmetal (C), 2
  metalloids (Si, Ge), and 2 metals (Sn,
  Pb)
 Contains elements important to life and
  computers.
 Carbon is the basis for an entire branch
  of chemistry.
 Coal and oil are mostly made of carbon.
 4 valence electrons
 Metallic nature increases from top to bottom (Ge is
  better conductor than Si)
 Life would not exist without carbon (except for
  water, most of the compounds in your body contain
  carbon)
 Reactions in your body controlled by carbon
  compounds
 Si is 2nd most abundant element in Earth’s crust
  (found in rocks, sand, and glass)
 Elements in group 15 (5A)
 Nitrogen makes up over ¾ of
  the atmosphere.
 Nitrogen and phosphorus are
  both important in living
  things.
 The red stuff on the tip of
  matches is phosphorus.
 5 valence electrons
 2 nonmetals, 2
  metalloids, and 1 metal
 Contain a wide range of
  physical properties
 Elements in group 16 (6A)
 Oxygen is necessary for
  respiration.
 Many things that stink,
  contain sulfur (rotten
  eggs, garlic, skunks, etc.)
 6 valence electrons
 3 nonmetals and 2 metalloids
 Oxygen is most abundant element in Earth’s crust


                           The 10 most
                           abundant elements
                           by mass in the
                           earth's crust . All
                           are main-group
                           elements except
                           iron and titanium.
 Elements in group 17 (7A)
 Very reactive, volatile,
  diatomic, nonmetals
 Always found combined
  with other element in
  nature .
 Used as disinfectants and
  to strengthen teeth.
 7 valence electrons
 Despite physical differences, the halogens have similar
  chemical properties
 Highly reactive nonmetals, with fluorine being the
  most reactive and chlorine a close 2nd
 React easily with most metals
 Chlorine added to drinking water and swimming
  pools to kill bacteria
 Elements in group 18 (8A)
 VERY unreactive,
  monatomic gases
 Used in blimps to fix the
  Hindenberg problem.
 Have a full valence shell.
 8 valence electrons
   EXCEPTION is Helium, it has 2 valence electrons
 Colorless and odorless
 Used in lighted “neon” signs

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:3
posted:10/25/2011
language:English
pages:68