The development of the periodic table is a project that will truly never end. The venture began with a household name of the scientific world, Dmitry Mendeleev. Mendeleev published the first actual periodic table in 1869; he pulled information and built upon earlier scientists’ work to create it.
The periodic table of elements is nothing more than a way to visually show the periodic law. The Periodic Law states that the physical and chemical properties of the elements recur in a systematic and predictable way when the elements are arranged in order of increasing atomic number. This is why the table is set up the way it is, by increasing atomic number, in that way, it’s easy to see the patterns.
The table itself is arranged by vertical columns (Called groups) and horizontal rows (Called periods). There are seven periods and 18 groups, each with their own name and reason they are grouped together.
The seven horizontal periods that stretch across the table make it so the elements with similar properties appear in the same vertical columns, or groups. Elements in the same period all have the same number of electron shells but as you go to the next group, staying in the same period the elements will have one more proton and are less metallic than the last.
The groups along the table are the horizontal rows, they each have a name and a specific set of characteristics. The names of the groups, going from left to right are; the alkali metals (lithium family), the alkaline earth metals (beryllium family), the scandium family, the titanium family, the vanadium family, the chromium family, the manganese family, the iron family, the cobalt family, the nickel family, the coinage metals (copper family), the zinc family, the triels (boron family), the tetrels (carbon family), the pnictogens (nitrogen family), the chalcogens (oxygen family), the halogens (fluorine family), and finally the noble gases (neon family). You’ll see most of the groups are named after a specific element. This is simply the first element in that group.
The periodic table is in constant, although extremely slow, motion. With the ongoing creation of elements being artificially synthesized in laboratories there is currently a debate on how exactly the table should be modified to fit the new elements. It’s generally understood that the same general form will be followed. If elements with a higher atomic number than 118 are discovered they will be placed in additional periods in a way that continues to show the patterns that the table now does.
It’s not possible to say, for now, exactly how many physical elements can exist, though many have tried. There has been a theoretical limit set at approximately 173 but it’s much more likely to center around 137. Different models have been used to try and determine the real number of elements but none have been conclusive.