History of the periodic table
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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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