atomic number e.g. number of protons
The heaviest element in the periodic table (known in March 2013) is ununoctium.
Today (June 2013) the periodic table contain 118 chemical elements, natural or artificial.
Not determined up today.
in ascending order by atomic number (number of protons) of an atom of a particular element. previously, the periodic table had elements ordered by atomic mass.
The element 120 was not obtained until today. The position will be probable in the group 2, under radium.
In 1869 when D. Mendeleev designed his periodic table any element in the period 7 was known. Today francium is in the group 1, period 7, atomic number 87.
Today 94 elements (1 to 94) are considered natural chemical elements.
Atomic Number
Chemists
Xe is the symbol for Xenon on the Periodic table. This is because in the latin language these are the first two letters of the element that are still used today.
In more than 150 years the periodic table had many versions; hundred versions of this table are known. The sole official table is today the IUPAC Periodic Table.
There are 91 metals in the periodic table today, but new ones are added as time passes.