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Chemical Periodicity

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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Chemical Periodicity

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  1. Chemical Periodicity

  2. 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

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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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