The Modern Periodic Table

Scientists continued to revise Mendeleev’s Periodic Table.

  • The Modern Periodic Table is arranged in order of increasing atomic number , rather than atomic weight.
  • there are now over 100 elements and no gaps in the Periodic Table.
  • a group of unreactive elements – the noble gases – were discovered at the end of the 1800s.
  • the modern Periodic Table includes transition metals, actinides and lanthanides.
Modern Periodic TableThe Modern Periodic Table
Each element in the Periodic Table is a substance that consists of only one type of atom. The elements cannot be broken down into simpler substances by chemical means.

Groups and periods

The modern table is called a “periodic” table because the elements with similar properties appear at regular intervals.

  • the vertical columns are called groups
  • the horizontal rows are called periods