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Periodicity

Periodicity. Periodic table and its importance. Elements are arranged in order of increasing atomic number and there is a periodicity in their physical and chemical properties. Atomic number (no. of electron). A. X . Z. Mass number (no. of neutron + proton).

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Periodicity

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  1. Periodicity

  2. Periodic table and its importance Elements are arranged in order of increasing atomic numberand there is a periodicity in their physical and chemical properties. Atomic number (no. of electron) A X Z Mass number (no. of neutron + proton)

  3. Horizontal rows = periods • There are 7 periods • Vertical column = group • Elements in the same group have the same chemical and physical properties.

  4. The Periodic table

  5. The Periodic table

  6. For example: Atomic Size In Periods • Going from left to right across a period, the size getssmaller. • Electrons are in the same energy level. • But, there is more nuclear charge. • Outermost electrons are pulled closer. Na S Cl Ar Al Si Mg P

  7. In Groups H • As we increase the atomic number (or go down a group) each atom has another energy level, so the atoms get bigger. Li Na K Rb

  8. A summary ofperiodicproperties and their variation in groups and periods is given below:

  9. As a practical example we take gp viiA ( halides) to study periodicity ( Cl-, Br-,I- )

  10. 1) Colour of the precipitate formed with silver nitrate 2) solubility of the formed precipitate in ammonia

  11. To test solubility ppt dissolve AgNO3 1 mLNaCl NH3 A white ppt of AgCl

  12. Add 1 ml AgNO3 to each tube 1 2 3 1 ml NaCl 1 ml NaBr 1 ml NaI Add 2 dps of the formed ppt. and shake gently Add 2 dps of the formed ppt. and shake gently Yellowish white precipitate Yellow precipitate White precipitate Slightly turbid solution (partially soluble ppt) Clear solution (soluble ppt) Turbid solution (insoluble ppt) Bring other 3 clean t.t and add 2ml dil NH3 to each one

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