Period 7 element

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A period 7 element is one of the chemical elements in the seventh row (or period) of the periodic table of the chemical elements. The periodic table is laid out in rows to illustrate recurring (periodic) trends in the chemical behavior of the elements as their atomic number increases: a new row is begun when chemical behavior begins to repeat, meaning that elements with similar behavior fall into the same vertical columns. The seventh period contains 32 elements, tied for the most with period 6, beginning with francium and ending with oganesson, the heaviest element currently discovered. As a rule, period 7 elements fill their 7s shells first, then their 5f, 6d, and 7p shells in that order, but there are exceptions, such as uranium.

Contents

Properties

All elements of period 7 are radioactive. This period contains the actinides, which includes plutonium, the naturally occurring element with the heaviest nucleus; [1] [note 1] subsequent elements must be created artificially. While the first five of these synthetic elements (americium through einsteinium) are now available in macroscopic quantities, most are extremely rare, having only been prepared in microgram amounts or less. The later transactinide elements have only been identified in laboratories in batches of a few atoms at a time.

Although the rarity of many of these elements means that experimental results are not very extensive, their periodic and group trends are less well defined than other periods. Whilst francium and radium do show typical properties of their respective groups, actinides display a much greater variety of behavior and oxidation states than the lanthanides. These peculiarities are due to a variety of factors, including a large degree of spin–orbit coupling and relativistic effects, ultimately caused by the very high positive electrical charge from their massive atomic nuclei. Periodicity mostly holds throughout the 6d series and is predicted also for moscovium and livermorium, but the other four 7p elements, nihonium, flerovium, tennessine, and oganesson, are predicted to have very different properties from those expected for their groups.

Elements

Chemical element Block Electron configuration Occurrence
 
87Fr Francium s-block [Rn] 7s1 From decay
88Ra Radium s-block [Rn] 7s2From decay
89Ac Actinium f-block [Rn] 6d1 7s2 (*)From decay
90Th Thorium f-block [Rn] 6d2 7s2 (*) Primordial
91Pa Protactinium f-block [Rn] 5f2 6d1 7s2 (*)From decay
92U Uranium f-block [Rn] 5f3 6d1 7s2 (*)Primordial
93Np Neptunium f-block [Rn] 5f4 6d1 7s2 (*)From decay
94Pu Plutonium f-block [Rn] 5f6 7s2From decay
95Am Americium f-block [Rn] 5f7 7s2 Synthetic
96Cm Curium f-block [Rn] 5f7 6d1 7s2 (*)Synthetic
97Bk Berkelium f-block [Rn] 5f9 7s2Synthetic
98Cf Californium f-block [Rn] 5f10 7s2Synthetic
99Es Einsteinium f-block [Rn] 5f11 7s2Synthetic
100Fm Fermium f-block [Rn] 5f12 7s2Synthetic
101Md Mendelevium f-block [Rn] 5f13 7s2Synthetic
102No Nobelium f-block [Rn] 5f14 7s2Synthetic
103Lr Lawrencium d-block [Rn] 5f14 7s2 7p1 (*)Synthetic
104Rf Rutherfordium d-block [Rn] 5f14 6d2 7s2Synthetic
105Db Dubnium d-block [Rn] 5f14 6d3 7s2Synthetic
106Sg Seaborgium d-block [Rn] 5f14 6d4 7s2Synthetic
107Bh Bohrium d-block [Rn] 5f14 6d5 7s2Synthetic
108Hs Hassium d-block [Rn] 5f14 6d6 7s2Synthetic
109Mt Meitnerium d-block [Rn] 5f14 6d7 7s2 (?)Synthetic
110Ds Darmstadtium d-block [Rn] 5f14 6d8 7s2 (?)Synthetic
111Rg Roentgenium d-block [Rn] 5f14 6d9 7s2 (?)Synthetic
112Cn Copernicium d-block [Rn] 5f14 6d10 7s2 (?)Synthetic
113Nh Nihonium p-block [Rn] 5f14 6d10 7s2 7p1 (?)Synthetic
114Fl Flerovium p-block [Rn] 5f14 6d10 7s2 7p2 (?)Synthetic
115Mc Moscovium p-block [Rn] 5f14 6d10 7s2 7p3 (?)Synthetic
116Lv Livermorium p-block [Rn] 5f14 6d10 7s2 7p4 (?)Synthetic
117Ts Tennessine p-block [Rn] 5f14 6d10 7s2 7p5 (?)Synthetic
118Og Oganesson p-block [Rn] 5f14 6d10 7s2 7p6 (?)Synthetic

(?) Prediction

(*) Exception to the Madelung rule.

In many periodic tables, the f-block is erroneously shifted one element to the right, so that lanthanum and actinium become d-block elements, and Ce–Lu and Th–Lr form the f-block tearing the d-block into two very uneven portions. This is a holdover from early erroneous measurements of electron configurations. [4] Lev Landau and Evgeny Lifshitz pointed out in 1948 that lutetium is not an f-block element, [5] and since then physical, chemical, and electronic evidence has overwhelmingly supported that the f-block contains the elements La–Yb and Ac–No, [4] [6] as shown here and as supported by International Union of Pure and Applied Chemistry reports dating from 1988 [6] and 2021. [7]

S-block

Francium and radium make up the s-block elements of the 7th period.

Francium(Fr, atomic number 87) is a highly radioactive metal that decays into astatine, radium, and radon. It is one of the two least electronegative elements, the other being caesium . As an alkali metal, it has one valence electron. Francium was discovered by Marguerite Perey in France (from which the element takes its name) in 1939. [8] It was the last element discovered in nature, rather than by synthesis. [note 2] Outside the laboratory, francium is extremely rare, with trace amounts found in uranium and thorium ores, where the isotope francium-223 continually forms and decays. As little as 20–30 g (one ounce) exists at any given time throughout Earth's crust; the other isotopes are entirely synthetic. The largest amount produced in the laboratory was a cluster of more than 300,000 atoms. [9]

Radium (Ra, atomic number 88) is an almost pure-white alkaline earth metal, but it readily oxidizes, reacting with nitrogen (rather than oxygen) on exposure to air, becoming black in color. All isotopes of radium are highly radioactive; the most stable isotope is radium-226, which has a half-life of 1601 years and decays into radon gas. Because of such instability, radium is luminescent, glowing a faint blue. Radium, in the form of radium chloride, was discovered by Marie and Pierre Curie in 1898. They extracted the radium compound from uraninite and published the discovery at the French Academy of Sciences five days later. Radium was isolated in its metallic state by Marie Curie and André-Louis Debierne through the electrolysis of radium chloride in 1910. Since its discovery, it has given names such as radium A and radium C2 to several isotopes of other elements that are decay products of radium-226. In nature, radium is found in uranium ores in trace amounts as small as a seventh of a gram per ton of uraninite. Radium is not necessary for living organisms, and adverse health effects are likely when it is incorporated into biochemical processes because of its radioactivity and chemical reactivity.

Actinides

The atomic bomb dropped on Nagasaki had a plutonium charge. Nagasakibomb.jpg
The atomic bomb dropped on Nagasaki had a plutonium charge.

The actinide or actinoid (IUPAC nomenclature) series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103, actinium through lawrencium. [11] [12] [13] [14]

The actinide series is named after its first element actinium. All but one of the actinides are f-block elements, corresponding to the filling of the 5f electron shell; lawrencium, a d-block element, is also generally considered an actinide. In comparison with the lanthanides, also mostly f-block elements, the actinides show much more variable valence.

Of the actinides, thorium and uranium occur naturally in substantial, primordial, quantities. Radioactive decay of uranium produces transient amounts of actinium, protactinium and plutonium, and atoms of neptunium are occasionally produced from transmutation reactions in uranium ores. The other actinides are purely synthetic elements, though the first six actinides after plutonium would have been produced at Oklo (and long since decayed away), and curium almost certainly previously existed in nature as an extinct radionuclide. [11] [15] Nuclear tests have released at least six actinides heavier than plutonium into the environment; analysis of debris from a 1952 hydrogen bomb explosion showed the presence of americium, curium, berkelium, californium, einsteinium and fermium. [16]

All actinides are radioactive and release energy upon radioactive decay; naturally occurring uranium and thorium, and synthetically produced plutonium are the most abundant actinides on Earth. These are used in nuclear reactors and nuclear weapons. Uranium and thorium also have diverse current or historical uses, and americium is used in the ionization chambers of most modern smoke detectors.

In presentations of the periodic table, the lanthanides and the actinides are customarily shown as two additional rows below the main body of the table, [11] with placeholders or else a selected single element of each series (either lanthanum or lutetium, and either actinium or lawrencium, respectively) shown in a single cell of the main table, between barium and hafnium, and radium and rutherfordium, respectively. This convention is entirely a matter of aesthetics and formatting practicality; a rarely used wide-formatted periodic table (32 columns) shows the lanthanide and actinide series in their proper columns, as parts of the table's sixth and seventh rows (periods).

Transactinides

Transactinide elements (also, transactinides, or super-heavy elements) are the chemical elements with atomic numbers greater than those of the actinides, the heaviest of which is lawrencium (103). [17] [18] All transactinides of period 7 have been discovered, up to oganesson (element 118).

Transactinide elements are also transuranic elements, that is, have an atomic number greater than that of uranium (92), an actinide. The further distinction of having an atomic number greater than the actinides is significant in several ways:

Transactinides are radioactive and have only been obtained synthetically in laboratories. None of these elements has ever been collected in a macroscopic sample. Transactinide elements are all named after nuclear physicists and chemists or important locations involved in the synthesis of the elements.

Chemistry Nobel Prize winner Glenn T. Seaborg, who first proposed the actinide concept which led to the acceptance of the actinide series, also proposed the existence of a transactinide series ranging from element 104 to 121 and a superactinide series approximately spanning elements 122 to 153. The transactinide seaborgium is named in his honor.

IUPAC defines an element to exist if its lifetime is longer than 10−14 seconds, the time needed for the nucleus to form an electronic cloud. [19]

Notes

  1. ↑ Trace quantities of 239Pu are found in uranium deposits [2] due to neutron capture of 238U and subsequent beta decay. It is also possible that the long-lived isotope 244Pu may exist primordially. [3]
  2. ↑ Some elements discovered through synthesis, such as technetium, have later been found in nature.

Related Research Articles

<span class="mw-page-title-main">Actinium</span> Chemical element with atomic number 89 (Ac)

Actinium is a chemical element; it has symbol Ac and atomic number 89. It was first isolated by Friedrich Oskar Giesel in 1902, who gave it the name emanium; the element got its name by being wrongly identified with a substance André-Louis Debierne found in 1899 and called actinium. Actinium gave the name to the actinide series, a set of 15 elements between actinium and lawrencium in the periodic table. Together with polonium, radium, and radon, actinium was one of the first non-primordial radioactive elements to be isolated.

<span class="mw-page-title-main">Americium</span> Chemical element with atomic number 95 (Am)

Americium is a synthetic chemical element; it has symbol Am and atomic number 95. It is radioactive and a transuranic member of the actinide series in the periodic table, located under the lanthanide element europium and was thus named after the Americas by analogy.

The actinide or actinoid series encompasses at least the 14 metallic chemical elements in the 5f series, with atomic numbers from 89 to 102, actinium through nobelium. The actinide series derives its name from the first element in the series, actinium. The informal chemical symbol An is used in general discussions of actinide chemistry to refer to any actinide.

A chemical element is a chemical substance that cannot be broken down into other substances by chemical reactions. The basic particle that constitutes a chemical element is the atom. Elements are identified by the number of protons in their nucleus, known as the element's atomic number. For example, oxygen has an atomic number of 8, meaning each oxygen atom has 8 protons in its nucleus. Atoms of the same element can have different numbers of neutrons in their nuclei, known as isotopes of the element. Two or more atoms can combine to form molecules. Chemical compounds are molecules made of atoms of different elements, while mixtures contain atoms of different elements not necessarily combined as molecules. Atoms can be transformed into different elements in nuclear reactions, which change an atom's atomic number.

Francium is a chemical element; it has symbol Fr and atomic number 87. It is extremely radioactive; its most stable isotope, francium-223, has a half-life of only 22 minutes. It is the second-most electropositive element, behind only caesium, and is the second rarest naturally occurring element. Francium's isotopes decay quickly into astatine, radium, and radon. The electronic structure of a francium atom is [Rn] 7s1; thus, the element is classed as an alkali metal.

Lawrencium is a synthetic chemical element; it has symbol Lr and atomic number 103. It is named in honor of Ernest Lawrence, inventor of the cyclotron, a device that was used to discover many artificial radioactive elements. A radioactive metal, lawrencium is the eleventh transuranic element and the last member of the actinide series. Like all elements with atomic number over 100, lawrencium can only be produced in particle accelerators by bombarding lighter elements with charged particles. Fourteen isotopes of lawrencium are currently known; the most stable is 266Lr with half-life 11 hours, but the shorter-lived 260Lr is most commonly used in chemistry because it can be produced on a larger scale.

Mendelevium is a synthetic chemical element; it has symbol Md and atomic number 101. A metallic radioactive transuranium element in the actinide series, it is the first element by atomic number that currently cannot be produced in macroscopic quantities by neutron bombardment of lighter elements. It is the third-to-last actinide and the ninth transuranic element. It can only be produced in particle accelerators by bombarding lighter elements with charged particles. Seventeen isotopes are known; the most stable is 258Md with half-life 51.59 days; however, the shorter-lived 256Md is most commonly used in chemistry because it can be produced on a larger scale.

<span class="mw-page-title-main">Periodic table</span> Tabular arrangement of the chemical elements ordered by atomic number

The periodic table, also known as the periodic table of the elements, is an ordered arrangement of the chemical elements into rows ("periods") and columns ("groups"). It is an icon of chemistry and is widely used in physics and other sciences. It is a depiction of the periodic law, which states that when the elements are arranged in order of their atomic numbers an approximate recurrence of their properties is evident. The table is divided into four roughly rectangular areas called blocks. Elements in the same group tend to show similar chemical characteristics.

<span class="mw-page-title-main">Thorium</span> Chemical element with atomic number 90 (Th)

Thorium is a chemical element. It has the symbol Th and atomic number 90. Thorium is a weakly radioactive light silver metal which tarnishes olive gray when it is exposed to air, forming thorium dioxide; it is moderately soft and malleable and has a high melting point. Thorium is an electropositive actinide whose chemistry is dominated by the +4 oxidation state; it is quite reactive and can ignite in air when finely divided.

The transuranium elements are the chemical elements with atomic numbers greater than 92, which is the atomic number of uranium. All of them are radioactively unstable and decay into other elements. With the exception of neptunium and plutonium which have been found in trace amounts in nature, none occur naturally on Earth and they are synthetic.

An extended periodic table theorizes about chemical elements beyond those currently known and proven. The element with the highest atomic number known is oganesson (Z = 118), which completes the seventh period (row) in the periodic table. All elements in the eighth period and beyond thus remain purely hypothetical.

A period 6 element is one of the chemical elements in the sixth row (or period) of the periodic table of the chemical elements, including the lanthanides. The periodic table is laid out in rows to illustrate recurring (periodic) trends in the chemical behaviour of the elements as their atomic number increases: a new row is begun when chemical behaviour begins to repeat, meaning that elements with similar behaviour fall into the same vertical columns. The sixth period contains 32 elements, tied for the most with period 7, beginning with caesium and ending with radon. Lead is currently the last stable element; all subsequent elements are radioactive. For bismuth, however, its only primordial isotope, 209Bi, has a half-life of more than 1019 years, over a billion times longer than the current age of the universe. As a rule, period 6 elements fill their 6s shells first, then their 4f, 5d, and 6p shells, in that order; however, there are exceptions, such as gold.

<span class="mw-page-title-main">Decay chain</span> Series of radioactive decays

In nuclear science, the decay chain refers to a series of radioactive decays of different radioactive decay products as a sequential series of transformations. It is also known as a "radioactive cascade". The typical radioisotope does not decay directly to a stable state, but rather it decays to another radioisotope. Thus there is usually a series of decays until the atom has become a stable isotope, meaning that the nucleus of the atom has reached a stable state.

Chemistry is the physical science concerned with the composition, structure, and properties of matter, as well as the changes it undergoes during chemical reactions.

<span class="mw-page-title-main">Group 3 element</span> Group of chemical elements

Group 3 is the first group of transition metals in the periodic table. This group is closely related to the rare-earth elements. It contains the four elements scandium (Sc), yttrium (Y), lutetium (Lu), and lawrencium (Lr). The group is also called the scandium group or scandium family after its lightest member.

Superheavy elements, also known as transactinide elements, transactinides, or super-heavy elements, or superheavies for short, are the chemical elements with atomic number greater than 103. The superheavy elements are those beyond the actinides in the periodic table; the last actinide is lawrencium. By definition, superheavy elements are also transuranium elements, i.e., having atomic numbers greater than that of uranium (92). Depending on the definition of group 3 adopted by authors, lawrencium may also be included to complete the 6d series.

<span class="mw-page-title-main">Actinides in the environment</span>

Environmental radioactivity is not limited to actinides; non-actinides such as radon and radium are of note. While all actinides are radioactive, there are a lot of actinides or actinide-relating minerals in the Earth's crust such as uranium and thorium. These minerals are helpful in many ways, such as carbon-dating, smoke detectors, X-rays, and more.

In nuclear chemistry, the actinide concept proposed that the actinides form a second inner transition series homologous to the lanthanides. Its origins stem from observation of lanthanide-like properties in transuranic elements in contrast to the distinct complex chemistry of previously known actinides. Glenn Theodore Seaborg, one of the researchers who synthesized transuranic elements, proposed the actinide concept in 1944 as an explanation for observed deviations and a hypothesis to guide future experiments. It was accepted shortly thereafter, resulting in the placement of a new actinide series comprising elements 89 (actinium) to 103 (lawrencium) below the lanthanides in Dmitri Mendeleev's periodic table of the elements.

A block of the periodic table is a set of elements unified by the atomic orbitals their valence electrons or vacancies lie in. The term seems to have been first used by Charles Janet. Each block is named after its characteristic orbital: s-block, p-block, d-block, f-block and g-block.

<span class="mw-page-title-main">Actinide chemistry</span> Branch of nuclear chemistry

Actinide chemistry is one of the main branches of nuclear chemistry that investigates the processes and molecular systems of the actinides. The actinides derive their name from the group 3 element actinium. The informal chemical symbol An is used in general discussions of actinide chemistry to refer to any actinide. All but one of the actinides are f-block elements, corresponding to the filling of the 5f electron shell; lawrencium, a d-block element, is also generally considered an actinide. In comparison with the lanthanides, also mostly f-block elements, the actinides show much more variable valence. The actinide series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103, actinium through lawrencium.

References

  1. ↑ "Periodic Table – Royal Society of Chemistry". www.rsc.org. Retrieved 2023-10-19.
  2. ↑ Miner, William N.; Schonfeld, Fred W. (1968). "Plutonium" . In Clifford A. Hampel (ed.). The Encyclopedia of the Chemical Elements. New York (NY): Reinhold Book Corporation. pp.  541. LCCN   68029938.
  3. ↑ Wu, Yang; Dai, Xiongxin; Xing, Shan; Luo, Maoyi; Christl, Marcus; Synal, Hans-Arno; Hou, Shaochun (2022). "Direct search for primordial 244Pu in Bayan Obo bastnaesite". Chinese Chemical Letters. 33 (7): 3522–3526. doi:10.1016/j.cclet.2022.03.036 . Retrieved 29 January 2024.
  4. 1 2 William B. Jensen (1982). "The Positions of Lanthanum (Actinium) and Lutetium (Lawrencium) in the Periodic Table". J. Chem. Educ. 59 (8): 634–636. Bibcode:1982JChEd..59..634J. doi:10.1021/ed059p634.
  5. ↑ L. D. Landau, E. M. Lifshitz (1958). Quantum Mechanics: Non-Relativistic Theory. Vol. 3 (1st ed.). Pergamon Press. pp. 256–7.
  6. 1 2 Fluck, E. (1988). "New Notations in the Periodic Table" (PDF). Pure Appl. Chem. 60 (3): 431–436. doi:10.1351/pac198860030431. S2CID   96704008. Archived (PDF) from the original on 25 March 2012. Retrieved 24 March 2012.
  7. ↑ Scerri, Eric (18 January 2021). "Provisional Report on Discussions on Group 3 of the Periodic Table" (PDF). Chemistry International. 43 (1): 31–34. doi:10.1515/ci-2021-0115. S2CID   231694898. Archived (PDF) from the original on 13 April 2021. Retrieved 9 April 2021.
  8. ↑ "Francium | Radioactive, Alkali Metal, Rare | Britannica". www.britannica.com. Retrieved 2023-10-19.
  9. ↑ Luis A. Orozco (2003). "Francium". Chemical and Engineering News.
  10. ↑ The Manhattan Project. An Interactive History. US Department of Energy
  11. 1 2 3 Gray, Theodore (2009). The Elements: A Visual Exploration of Every Known Atom in the Universe. New York: Black Dog & Leventhal Publishers. p.  240. ISBN   978-1-57912-814-2.
  12. ↑ Actinide element, Encyclopædia Britannica on-line
  13. ↑ Although "actinoid" (rather than "actinide") means "actinium-like" and therefore should exclude actinium, that element is usually included in the series.
  14. ↑ Connelly, Neil G.; et al. (2005). "Elements". Nomenclature of Inorganic Chemistry. London: Royal Society of Chemistry. p. 52. ISBN   978-0-85404-438-2.
  15. ↑ Greenwood, p. 1250
  16. ↑ Fields, P.; Studier, M.; Diamond, H.; Mech, J.; Inghram, M.; Pyle, G.; Stevens, C.; Fried, S.; Manning, W. (1956). "Transplutonium Elements in Thermonuclear Test Debris". Physical Review. 102 (1): 180. Bibcode:1956PhRv..102..180F. doi:10.1103/PhysRev.102.180.
  17. ↑ IUPAC Provisional Recommendations for the Nomenclature of Inorganic Chemistry (2004) Archived 2006-10-27 at the Wayback Machine (online draft of an updated version of the "Red Book" IR 3–6)
  18. ↑ Morss, Lester R.; Edelstein, Norman M.; Fuger, Jean, eds. (2006). The Chemistry of the Actinide and Transactinide Elements (3rd ed.). Dordrecht, The Netherlands: Springer. ISBN   978-1-4020-3555-5.
  19. ↑ "Kernchemie".
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