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History of the Periodic Table. Dimitri Mendeleev published a periodic table that arranged elements by increasing atomic mass This did not accurately group elements by similar properties The modern table is arranged by increasing atomic number

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history of the periodic table
History of the Periodic Table
  • Dimitri Mendeleev published a periodic table that arranged elements by increasing atomic mass
  • This did not accurately group elements by similar properties
  • The modern table is arranged by increasing atomic number
  • Periodic Law – there is a periodic repetition of physical and chemical properties when elements are arranged by increasing atomic number

Some of Medeleev’s work (1869)

periodic table a review
Periodic Table (a review)
  • Groups go down the table
  • Elements in the same group have similar properties
  • Periods go across the table
  • Chemical properties of the elements change in a predictable manner going across a period
periodic table review cont
Periodic Table review (cont)
  • Group 1A – alkali metals
  • Group 2A – alkaline earth metals
  • Group 6A - chalcogens
  • Group 7A – halogens
  • Group 8A – noble gases
  • Metals are to the left of the staircase
  • Non-metals are to the right of the staircase
  • Metalloids are along the staircase (B, Si, Ge, As, Sb, Te, Po)
periodic trends
Periodic Trends
  • Atomic radius
  • Ionization energy
  • Electronegativity
atomic radius
Atomic Radius
  • The size (radius) of an atom of that element
  • Increases moving down a group
  • Decreases moving from left to right across a period
ionization energy
Ionization Energy
  • Amount of energy needed to remove an e- from an atom to form an ion
  • Decreases moving down a group
  • Increases moving from left to right across a period
ions atoms with a charge
IONS --> Atoms with a charge

Lithium Ion

Lithium Atom

3+

3-

2-

0 charge

+1 charge

3+

The ionization energy

is the amount of energy

needed to remove this e-

octet rule and ions
Octet rule and ions
  • Atoms with a filled outer energy level (stable octet) are more stable
  • Atoms lose/gain electrons in an effort to obtain a filled outer energy level.
  • Anions (- ions) form by an atom gaining e-
  • Cations (+ ions) form by an atom losing e-
electronegativity
Electronegativity
  • The ability of an atom to attract electrons in a chemical bond
  • Increases moving from left to right across a period
  • Decreases going down a group
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