Periodic table of elements; SCIENCE

• Element - PURE SUBSTANCE that is made out of a single type of atom
• There are 118 elements in the periodic table
• The periodic table was classified into two elements before namely: Metals and Nonmetals
• Johann Wolfgang Dobereiner

  • “Dobereiner triads”
  • classified SIMILAR ELEMENTS into groups of THREE called triads
• John Newlands

  • “Newlands law of Octaves
  • Arranged the elements according to INCREASING ATOMIC MASS
• Dmitri Mendeleev

  • “Mendeleevs periodic table”
  • arranged the elements in VERTICAL COLUMNS
• Henry Moseley

  • Developer of the Modern periodic table
  • Arranged the elements according to INCREASING ATOMIC NUMBER
• Groups or Families - VERTICAL COLUMNS that contains elements with similar properties
• Period - HORIZONTAL ROWS in the periodic table
• metals - left side
• non-metals - right side
• Stair step line - separates metals & non-metals
• Semi-metals - elements along the stair step line
• Semi-metals - have the appearance and some properties of a metal but behave like a non-metal