Prescription painkillers, also known as opioid pain relievers, include oxycodone, hydrocodone, hydromorphone, and others. Many people who abuse these painkillers become dependent. Some even move on to abusing illegal narcotics, such as heroin.
The first 92 (through uranium) occur naturally. The others are transuranics.. As of 2009, there are 118 ending with ununoctium. All together there are 117 elements on the periodic table, 94 of which occur naturally on earth. According to Wikipedia, there are 117 elements that have been isolated or synthesized, with a gap between element 116 and element 118.
There are 18 columns on the periodic table. The first 2, and 13-18 are all grouped by how many valence electrons the outermost ring of an atom has. Therefore, the elements in the columns all have similar properties. There are also other ways they are grouped. They are arranged in number order.