Roentgenium

Roentgenium

Roentgenium is a synthetic radioactive chemical element with the symbol Rg and atomic number 111. It is placed as the heaviest member of the group 11 elements, although a sufficiently stable isotope has not yet been produced in a sufficient amount that would confirm this position as a heavier...

(Rg) is an artificial element, and thus a standard atomic mass

Atomic mass

The atomic mass is the mass of a specific isotope, most often expressed in unified atomic mass units. The atomic mass is the total mass of protons, neutrons and electrons in a single atom....

 cannot be given. Like all artificial elements, it has no stable isotope

Stable isotope

Stable isotopes are chemical isotopes that may or may not be radioactive, but if radioactive, have half-lives too long to be measured.Only 90 nuclides from the first 40 elements are energetically stable to any kind of decay save proton decay, in theory...

s. The first isotope

Isotope

Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...

 to be synthesized was ²⁷²Rg in 1994, which is also the only directly synthesized isotope, all others are decay product

Decay product

In nuclear physics, a decay product is the remaining nuclide left over from radioactive decay. Radioactive decay often involves a sequence of steps...

s of ununtrium

Ununtrium

Ununtrium is the temporary name of a synthetic element with the temporary symbol Uut and atomic number 113.It is placed as the heaviest member of the group 13 elements although a sufficiently stable isotope is not known at this time that would allow chemical experiments to confirm its position...

, ununpentium

Ununpentium

Ununpentium is the temporary name of a synthetic superheavy element in the periodic table that has the temporary symbol Uup and has the atomic number 115....

, and ununseptium

Ununseptium

Ununseptium is the temporary name of a superheavy artificial chemical element with temporary symbol Uus and atomic number 117. Six atoms were detected by a joint Russia–US collaboration at Dubna, Moscow Oblast, Russia, in 2009–10...

. There are 7 known radioisotopes from ²⁷²Rg to ²⁸²Rg. The longest-lived isotope is ²⁸¹Rg with a half-life

Half-life

Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...

 of 26 seconds.

Table

nuclide symbol	Z(p Proton The proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number.... )	N(n Neutron The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of... )	isotopic mass (u)	half-life	decay mode(s)Abbreviations: SF: Spontaneous fission Spontaneous fission Spontaneous fission is a form of radioactive decay characteristic of very heavy isotopes. Because the nuclear binding energy reaches a maximum at a nuclear mass greater than about 60 atomic mass units , spontaneous breakdown into smaller nuclei and single particles becomes possible at heavier masses...	daughter isotope(s)	nuclear spin
272Rg	111	161	272.15362(36)#	2.0(8) ms [3.8(+14-8) ms]	α Alpha decay Alpha decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle and thereby transforms into an atom with a mass number 4 less and atomic number 2 less...	268Mt	5+#,6+#
274RgNot directly synthesized, occurs as a decay product Decay product In nuclear physics, a decay product is the remaining nuclide left over from radioactive decay. Radioactive decay often involves a sequence of steps...  of 278Uut	111	163	274.15571(66)#	6.4(+307-29) ms	α	270Mt
278RgNot directly synthesized, occurs as a decay product of 282Uut	111	167	278.16160(68)#	1# s	α	274Mt
279RgNot directly synthesized, occurs in decay chain Decay chain In nuclear science, the decay chain refers to the radioactive decay of different discrete radioactive decay products as a chained series of transformations...  of 287Uup	111	168	279.16247(71)#	0.17(+81-8) s	α	275Mt
280RgNot directly synthesized, occurs in decay chain of 288Uup	111	169	280.16447(80)#	3.6(+43-13) s	α	276Mt
281RgNot directly synthesized, occurs in decay chain of 293Uus	111	170	281.16537(100)#	26 s	SF Spontaneous fission Spontaneous fission is a form of radioactive decay characteristic of very heavy isotopes. Because the nuclear binding energy reaches a maximum at a nuclear mass greater than about 60 atomic mass units , spontaneous breakdown into smaller nuclei and single particles becomes possible at heavier masses...	(various)
282RgNot directly synthesized, occurs in decay chain of 294Uus	111	171	282.16749(95)#	0.5 s	α	278Mt

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.