Dmitri Mendeleev
Iron.
7
Calcium
Periodical chart
Because it is an element.
alkaline earth metals
Na is an element found on the periodical table. It is the chemical symbol for Sodium.
Sulphur/ Sulfur --> S (in capital letter) in the periodic table
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.
For halogens this is the only way to react as oxidant.