Introduction to The Periodic Table

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Introduction to The Periodic Table
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Introduction

• More than 110 elements are known.
• Around 90 elements occur naturally while others
  are made artificially.
• Elements vary greatly in their physical and
  chemical properties.

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Father of the Periodic Table

• Demitri Mendeleev ( Russian Chemist)

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• Mendeleev arranged the elements in order of
  atomic mass.
• Then he observed similar chemical and physical
  properties appear at regular, or periodic
  intervals.

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The Modern Periodic Table

• In modern periodic table, the elements are
  arranged in order of atomic number and electron
  configuration.

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Periodic Law

• The properties of the elements are periodic
  function of their atomic number.

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Periodic Table
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Arrangements of the Periodic table

• Period the horizontal rows of the table.
• The period number is the number of energy levels
  in which electrons occupy in the atom of an
  element.

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Groups / Families

• Groups the vertical columns of the table.
• Each member of a given group contains the same
  number of valence electron.

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Valence electrons

• The electrons in the outer energy levels of an
  atom.
• e.g. 2-8-7
• valence electrons
• The last number in the electron configuration

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• Across a period, the properties of elements
  change systematically.
• Na very reactive metal
• Mg reactive metal
• Al - less reactive metal
• Si - metalloid
• P - reactive non-metal
• S reactive non-metal
• Cl Very reactive non-metal
• Ar noble gas

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• Elements in the same group have similar
  properties because it is the number of valence
  electrons that determines the chemical properties
  of the element.

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Special Groups

• Group 1 Alkaline metals
• Group 2 Alkaline earth metals
• Group 17 Halogens
• Group 18 Noble gases
• Groups 3-12 - Transition metals

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Ions

• Ions are charge particles while atoms are
  neutral.
• There are two types of ions.
• 1. Positive ions Cations
• 2. Negative ions - Anions

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Formation of Ions

• Cations cations are formed when metals lose
  electrons.
• E.g. Na (2-8-1) Na (2-8) e
• Anions Anions are formed when non-metals gain
  electrons.
• E.g. Cl (2-8-7) e Cl (2-8-8)

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