about 106 are on a Periodic Table for the very time being
Dmitri Mendeleev
Iron.
Calcium
Periodical chart
Because it is an element.
Na is an element found on the periodical table. It is the chemical symbol for Sodium.
it is 56 because you round it of and it used to be 55.85
There are 117 elements in the periodic table. Elements 1-116 and element 118. IMPROVED ANSWER --------------------------------------------------------------------------------------- 118, but element 117 is so unstable they do not officially count it as being an element on the periodic table yet.
Sulphur/ Sulfur --> S (in capital letter) in the periodic table
For halogens this is the only way to react as oxidant.
The chemical symbol for Mercury is Hg. The atomic number for the element is 80. It is one of the only liquid elements on the table.
Ar stand for Argon, a noble gas of group 8 in periodical table.