Facts about the periodic table:
- Elements are arranged in horizontal rows called periods in order of increasing (proton) number
- The number of electron shells is the same as the period number
- Elements with the same number of outermost electrons are arranged in vertical columns called groups
- The number of outermost electrons is the same as the group number
- Properties within each individual group are similar, but vary slightly
- Generally, chemical activity decreases as the period increases a non-metal group and increases as the period increases within a metal group
The history:
Dimitri Mendeleev, the inventor and father of the periodic table, percieved the correct classification method "the periodic table" for the 65 elements known in his time by their atomic weights and chemical valency. Mendeleev then went further, using the remaining gaps and spaces in his periodic table, and concluded that a group of yet unknown elements must exist to fill up the gaps in the periodic table.
Fifty years after Dimitri Mendeleev created the periodic table, british scientist Henry Moseley discovered that the number of protons in the nucleus of a particular type of atom was always the same. When the atoms are arranged via their atomic number, the few remaining problems with Mendeleev's original periodic table disappeared. Due to Moseleys's work, the modern periodic table is based on the atomic numbers of the elements rather than the mass.
Henry Moseley:
Fun Facts
Did you know that the only letter not appearing in the periodic table is
"j"?
