These elements are called metalloids. On the periodic table, metalloids can be found starting at Boron going down and to the right in a zig-zag pattern. Elements that are metalloids are Boron, Silicon, Germanium, Arsenic, Antimony, Tellurium, and Polonium.
The difference between naturally occuring and synthetic elements is that synthetic elements can't be found naturally - they can only be synthesised by man. Elements after no. 92 (Uranium) are all synthetic.
On the periodic table, the elements borders the zigzag lines are called metalloids. They also are referred to as semi-conductors. Metalloids are elements having properties intermediate between those of a metal and a nonmetal. Some metalloids are silicon, antimony, boron, and tellurium.
On the periodic table there is a zigzag line (staircase) running along group 13 to group 16. Metalloids are the elements along the staircase. The six elements commonly recognized as metalloids are boron, silicon, germanium, arsenic, antimony and tellurium.
On the periodic table, there is usually a dark stair-step line running from boron to polonium. That line shows where the metalloids are on the periodic table. To the left of the metalloids are the elements that are metals and to the right of the metalloids are the elements that are the non-metals.