History of the Periodic Table Chapter 6

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History of the Periodic TableChapter 6
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Dobereiner

• First person to create reasonably accurate
  measurements for atomic mass.

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Newlands

• In 1864, Newlands proposed an organization scheme
  for the elements
• By arranging them in order of increasing atomic
  mass, he realized that their properties repeated
  every eighth element.
• He called this periodicity the Law of Octaves.
• Acceptance of his arrangement wasnt immediate
  because it didnt work universally in predicting
  chemical properties.

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Meyer Mendeleev

• In 1869, Lothar Meyer demonstrated a connection
  between atomic mass and elemental properties.
• In 1869, a Russian chemist named Dimitri
  Mendeleev also came up with a way of organizing
  the elements that were known at the time.
• Both chemists set the elements out in order of
  atomic mass
• Both then grouped them into rows and columns
  based on their chemical and physical properties.
• Mendeleev predicted the existence and properties
  of undiscovered elements, which is largely why
  his table got such wide acceptance.

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Mendeleevs Early Periodic Table, Published in
1872
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Moseley

• Instead of ordering elements by total atomic
  mass, order by proton (atomic) number.
• This creates some minor shufflings in Mendeleevs
  table and allows us to better predict unknown
  elements.

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The Modern Periodic TableChapter 6
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Arrangement and Nomenclature

• Rows are called periods
• Columns are designated as groups
• Each column in the main table and each row at the
  bottom is also designated an individual family
• Groups 1A, 2A, and 3-8A are the main groups, or
  representative elements
• Groups 1B-8B are called the transition elements

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The Periodic Table With Atomic Symbols, Atomic
Numbers, and Partial Electron Configurations
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Broad Periodic Table Classifications

• Representative Elements (main group) filling s
  and p orbitals (Na, Al, Ne, O)
• Transition Elements filling d orbitals (Fe,
  Co, Ni)
• Lanthanide and Actinide Series (inner transition
  elements) filling 4f and 5f orbitals (Eu, Am,
  Es)

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Information Contained in the Periodic Table

1. Each group member has the same valence electron
   configuration (these electrons primarily
   determine an atoms chemistry).
2. The electron configuration of any representative
   element.

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Information Contained in the Periodic Table

• Certain groups have special names (alkali metals,
  alkaline earth metals, chalcogens, halogens,
  etc).
• Metals and nonmetals are characterized by their
  chemical and physical properties.

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Special Names for Groups in the Periodic Table
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Metals

• Metals makeup more than 75 of the elements in
  the periodic table. Metals are characterized by
  the following physical properties
• They have metallic shine or luster.
• They are usually solids at room temperature.
• They are malleable. Malleable means that metals
  can be hammered, pounded, or pressed into
  different shapes without breaking.
• They are ductile meaning that they can be drawn
  into thin sheets or wires without breaking.
• They are good conductors of heat and electricity.

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Metals (cont)

• All B and most A elements are metals.
• The B ? At stairstep designates the border
  between metals and non-metals
• 1A elements are alkali metals
• They are soft shiny metals that usually combine
  with group VIIA nonmetals in chemical compounds
  in a 11 ratio.
• 2A elements are the alkaline earth metals
• Both alkali and alkaline earth metals are
  chemically reactive, but 2A metals are less
  reactive than 1As.
• They combine with the group VIIA nonmetals in a
  12 ratio.

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Transition Metals Metalloids

• Transition metals
• The remaining 1-8B elements are all transition
  elements
• The transition elements also have valence
  electrons in two shells instead of one.
• Inner transition metals
• The lanthanide and actinide series comprise the
  inner transition metals

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Metalloids

• Metalloids have characteristics of both metals
  and nonmetals and so cant be classified as
  either, but something in between.
• They are good conductors of heat and electricity
• They are not good conductors or insulators.
• The six metalloids are B, Si, Ge, As, Sb, and Te.

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Nonmetals

• There are 17 nonmetals in the periodic table, and
  they are characterized by four major physical
  properties.
• They rarely have metallic luster.
• They are usually gases at room temperature.
• Nonmetallic solids are neither malleable nor
  ductile.
• They are poor conductors of heat and electricity.
• The elements above the B ? At stairstep are
  nonmetals

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Nonmetals (cont)

• Group 6A contains the chalcogen elements
• Group 7A contains the highly reactive halogen
  elements
• They are fluorine, chlorine, bromine, and iodine.
  
• The halogens exist as diatomic molecules in
  nature.
• Group 8A comprises the completely non-reactive
  noble gases
• The noble gases are also called rare gas
  elements, and they all occur in nature as gases.
• The noble gases fulfill the octet rule by having
  a full outer level with 8 valence electrons.
• Therefore, they do not undergo chemical reactions
  because they do not accept any electrons.

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Valence Electrons and the Periodic Table

• Valence Electrons and Group
• Atoms in the same group have the same chemical
  properties because they have the same number of
  valence electrons.
• Moreover, they have the same outermost orbital
  structure
• E.g. 1A elements all have s1 valence electrons
• E.g. 2A elements all have s2 valence electrons
• Valence Electrons and Period
• The primary quantum number (n) for an elements
  valence electrons is the same its period.
• E.g. Lithiums valence electron is n2 and Li is
  found in the 2nd period

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The Octet Rule

• Atoms tend to lose, gain, or share electrons
  until they are surrounded by 8 valence electrons