Chapter 5 The Periodic Table

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Chapter 5The Periodic Table
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Discovery of the Elements

• Many elements known since ancient times
• Gold
• Silver
• Copper
• Mercury

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Discovery of the Elements

• 1649
• First scientific discovery of an element
• Hennig Brand discovered phosphorus
• 200 years of discovery and knowledge-gathering
  followed
• 1869
• Total of 63 elements had been discovered
• Scientists began recognizing patterns in
  properties and developed classification schemes

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Johann Dobereiner (1817)

• German Chemist
• Proposed that nature contained triads of elements
• Law of Triads
• The middle element had properties that were an
  average of the other two members when ordered by
  the atomic weight

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E. Beguyer de Chancourtois (1863)

• 44 year old French Geologist
• Transcribed the list of elements positioned in a
  cylinder in terms of increasing atomic weight
• 16 mass units per turn
• closely related elements lined up vertically
• First geometric representation of periodic law
• first to recognize elemental properties reoccur
  every seven elements
• Errors his chart included ions and compounds

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John A. R. Newlands (1863)

• 32 year old English Chemist
• wrote a paper classifying the 56 established
  elements into 11 groups based on similar physical
  properties
• Proposed Law of Octaves
• Musical scale
• Any given element will exhibit behavior analogous
  to the 8th element following it in the table
• Ignored by English Chemical Society
• (ideas absurd)

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Two men working independently about the same time
published periodic tables which are very
similarhowever only 1 is recognized as the
Father of the Periodic Table. Why???

• Mendeleev published first
• Meyer did not leave room for elements yet
  undiscovered but Mendeleev did

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Lothar Meyer (1868-1870)

• German Chemist
• Published periodic table that was accurate for
  all elements known at the time
• Based upon facts about each element
• Melting point
• Atomic volume
• Showed existence of periodic chemical families
• Was not known publicly until 1870

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Dmitri Ivanovich Mendeleev

• 35 year old Russian scientist and professor (born
  1834, died 1907)
• published table in 1869

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Dmitri Ivanovich Mendeleev

• Showed periodic chemical families based upon
  known facts (like Meyer) but also left gaps for
  elements not yet discovered
• Shows vertical, horizontal, diagonal
  relationships
• Predicted what properties those undiscovered
  elements would have and what state (solid,
  liquid, gas) they would most likely be in
• For most of his predictions he was amazingly
  accurate!

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Noble Gas Discoveries

• Lord Rayleigh (1895)
• Discovered new gaseous element named argon
  (chemically inert)
• Did not fit any of the known periodic groups
• William Ramsey (1898)
• Suggested argon be placed into the periodic table
  between chlorine and potassium in a family with
  helium
• This went against atomic weights
• Group was termed the zero group due to
  unreactiveness
• Accurately predicted future discovery and
  properties of neon

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Ernest Rutherford andHenry Moseley (1911-1913)

• Established atomic number
• positively charged protons
• Reordered the periodic table based on atomic
  numbers instead of atomic weights
• PERIODIC LAW
• when elements are arranged in order of increasing
  atomic number their physical and chemical
  properties show a periodic pattern

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Periodic Tables Today
Dr. Timothy Stowes physicists periodic table
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Periodic Tables Today
The periodic spiral of Professor Theodor Benfey
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Periodic Tables Today
A triangular long form periodic table by Emil
Zmaczynski
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Periodic Tables Today
Albert Tarantolas orbital periodic table
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5-2Reading The Periodic Table

• If you know how the periodic table is
  arrangedyou can predict the properties of an
  element by knowing its location

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Families or Groups

• Columns
• Elements with similar properties
• 18 groups

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Periods or Rows

• across the table
• 7 periods
• How many elements in each?
• Period 1
• Period 2
• Period 3
• Period 4
• Period 5
• Period 6
• Period 7

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WHY???
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18
32
Could be 32 if known
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Naming of Groups (Families)

• European (Roman)
• American (Roman, now Arabic numerals)
• IUPAC tried to resolve 2 systems

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Names of Groups

• Alkali metals 1
• Alkaline earth metals 2
• Transition metals all d-block families (groups
  3-12)
• Inner transition metals all f-block families
• Halogens 17
• Noble gases 18
• Some named after first element in group
• B, C, O, N (groups 13-16)

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METALS

• (p166-167 light blue)
• Conduct heat and electricity
• Solids (except Hg)
• Malleable and ductile
• Have luster or shine

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NONMETALS

• (p166-167 pink)
• No luster
• Not malleable
• Poor conductors
• Not ductile
• Most are gases at Room temperature (but some
  solids and one liquid)

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METALLOIDS

• (p166-167 purple)
• Semimetals
• Diagonal between metals and nonmetals
• Share properties

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Electron Configuration and Periodic Table

• Valence Electrons
• Electrons responsible for an elements chemical
  behavior
• outermost electrons
• Elements of a family have similar properties
  because they have valence electrons in similar
  configuration

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Electron Configuration and Periodic Table

• Key to shape ? arranged by electron
  configuration
• s-block p-block d-block f-block
• Look at abbreviated configuration
• Use Noble gas symbol
• Lithium 1s22s1 or He2s1
• Sodium 1s22s22p63s1 or Ne3s1

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5-3 Periodic Trends

• Many properties of the elements change in a
  predictable way as you move through the periodic
  table

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Atomic Radius

• distance from center of nucleus to outermost
  electrons
• Hard to determine use distance between nuclei in
  different atoms of different molecules (a)
• Ex Cl2 (two chlorine atoms bonded)

a 0.198 nm Soradius of one Cl is 0.198/2
0.99 nm
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Atomic Radius

• Atoms get larger down a group due to increase in
  of protons, neutrons, and electrons
• Atoms get smaller in each period (left ? right)
• WHY???

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Atomic Radius

• Moving down a family
• As quantum number increases the number of
  electrons increases
• Size increases
• Moving across a period
• Gain protons
• More protons means greater pull on electrons
• smaller Radius

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Ionic Size

• Remember, an ion is an atom that has GAINED or
  LOST electrons
• When atom loses e- it becomes smaller
• Ex Li 0.152nm ? Li 0.060nm
• Due to decreased repulsion between electrons
• When atom gains e- it becomes larger
• Ex F 0.064nm ? F- 0.136nm
• Due to increased repulsion between electrons

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• Elements within the SAME FAMILY form ions with
  the SAME CHARGE
• Li Na K Rb Cs etc

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Ionization Energy

• energy needed to REMOVE one of an atoms electrons
• Li ? Li e- 8.64 10-19 joules/atom
• Usual unit
• KJ/mole
• Ionization energy 521 kJ/mol
• Mole is a quantity of atoms

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Ionization Energy

• How strongly an atom HOLDS ONTO its outermost
  electrons
• ? Ionization Energy hold tightly to electrons
  gains electrons becomes NEGATIVELY charged
• Ionization Energy hold loosely to electrons
  loses electrons becomes POSITIVELY charged

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Electronegativity

• Reflects an atoms ability to ATTRACT electrons
  in a chemical bond
• Flourine most electronegative with a value of
  4.0
• Cs and Fr least electronegative with values of
  0.7

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• Ionization Energy and Electronegativity have
  similar trends

INCREASES