Chemical periodicity
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Chemical Periodicity. History. Dmitri Mendeleev (1834 – 1907) Russian chemist Noticed regular (periodic) recurrence of chemical and physical properties after arranging by increasing atomic mass. Eventually led to grouping by similar properties side by side

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History
History

  • Dmitri Mendeleev (1834 – 1907)

    • Russian chemist

    • Noticed regular (periodic) recurrence of chemical and physical properties after arranging by increasing atomic mass.

      • Eventually led to grouping by similar properties side by side

        Predicted properties of then unknown elements with amazing accuracy.

  • Henry Mosely(1887 – 1915)

    • British physicist

    • Identified atomic number (nuclear charge) of the atoms of elements

      • Arranged periodic table by atomic number

        Current arrangement of periodic table


The periodic table
The Periodic Table

  • Periods – horizontal rows of the periodic table.

  • Groups – vertical columns of the periodic table.

  • Periodic Law – when the elements are arranged in order of increasing atomic number, there is a periodic pattern in their physical and chemical properties.


Electron configuration periodicity
Electron Configuration/Periodicity

  • Noble gases

    • Outermost p and s sublevels are filled

  • Representative elements

    • Outermost p and s sublevels are only partially filled

    • Called the Group A elements

      • Alkali metals – group 1A

      • Alkaline earth metals – group 2A

      • Halogens – group 7A

  • Transition metals

    • Outermost s sublevel and the nearby d sublevel contains electrons

    • Called the group B elements

  • Inner transition metals

    • Outermost s sublevel and the nearby f sublevel generally contain electrons


Atomic radius
Atomic Radius

  • = half the distance between the nuclei of two like atoms.

  • Atomic size generally increases as you move down a group.

  • Atomic size generally decreases as you move from left to right across a period.

    Largest atoms are towards the bottom and to the left of the periodic table.


Ionization energy
Ionization Energy

  • = The energy that is required to overcome the attraction of the nuclear charge and remove an electron from a gaseous atom.

  • Ionization energy decreases as you move down a group of the periodic table.

  • For the representative elements, ionization energy generally increases as you move from left to right across a period.


Electronegativity
Electronegativity

  • = the tendency for the atoms of the element to attract electrons when they are chemically combined with another element.

  • Electronegativity increases for the representative elements as you move from left to right and generally decreases as you move down a group.


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