could be either the atomic number or the mass number of the element, depending on what you are referring to.
Arsenic, or As, has the atomic number of 33.
There were 102 known elements on the periodic table in 1960.
Ci means chlorine in the periodic table
Helium
Iodine
Oxygen,
a family of the periodic table is like a group of elements of the same type.
Er means erbium in the periodic table. It belongs to lanthanide series.
Mo stands for Molybednium in the periodic table. It is placed in group-6.
what ploh does mean
calcium
The only thing it might mean would be number, but that is usually no. and not NO. NO would be nitrogen oxide (nitric oxide), but that would NOT appear in the periodic table, as it is a compound, and only ELEMENTS appear in the periodic table.