Periodic table Notes #4 In 1869, Dmitri Mendeléev created the first accepted version of the periodic table. He grouped elements according to their atomic mass, and as he did, he found that the families had similar chemical properties.  Families are the vertical columns (also called groups) Elements in families have the same number of valence electrons Periods are the horizontal rows Elements in the periods have the same number of orbitals or electron shells Blank spaces were left open to add the new elements he predicted would occur… and they did!

Periodic table Elements in the same family (column) have the same properties. Each family has a name. The numbers for families are found at the top of the chart. (1-8) Elements in the same Period (row) have the same amount of orbital (or electron shells) The numbers for the periods are found on the left side (1-7) The Periodic table is also divided into 4 categories: Metals, non- metals, metalloids and Noble gasses. You can explore the families and categories by going to http://www.ptable.com/