How many elements are on the periodic table?

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Accepted Answer

There are 118 elements on the periodic table , so the number of chemical elements in the modern periodic table is 118, running from hydrogen (atomic number 1) to oganesson (atomic number 118). Each element is defined by its atomic number, the count of protons in its nucleus, which is why there are no gaps and no repeats. All 118 known elements are confirmed and named by IUPAC. About 94 occur in nature, at least in trace amounts, and the other 24, elements 95 to 118, are synthetic elements made in reactors or particle accelerators. The natural count depends on the definition: 80 elements have a stable isotope, 83 are primordial, and 90 appear once the decay products of uranium and thorium, such as radon and polonium, are included. The seven periods (rows) hold 2, 8, 8, 18, 18, 32 and 32 elements, and the 18 groups (columns) sort them into families such as the alkali metals, halogens and noble gases. For comparison, Mendeleev's first table in 1869 listed 63 known elements. No element beyond 118 has been confirmed, so the table stays complete until an element 119 is made and accepted by an international review, which can take years. Counted by block, there are 14 s-block, 36 p-block, 40 d-block and 28 f-block elements, with lutetium and lawrencium placed in the d-block. At room temperature 11 elements are gases, 2 are liquids (mercury and bromine) and 90 are solids, while the state of the 15 heaviest, elements 104 to 118, has not been measured. By family on this site there are 38 transition metals, 15 lanthanides, 15 actinides, 12 post-transition metals, 7 reactive nonmetals, 7 noble gases and 6 each of alkali metals, alkaline earth metals, metalloids and halogens. The newest names, nihonium, moscovium, tennessine and oganesson, were approved in 2016 and completed period 7. In short, 118 different elements are known to science today, and the number only grows when a new element is confirmed.