Group 1 elements
| ← 1Family → | |
| Period | |
| 1 | 1 H |
| 2 | 3 Li |
| 3 | 11 Na |
| 4 | 19 K |
| 5 | 37 Rb |
| 6 | 55 Cs |
| 7 | 87 Fr |
The element which belongs to the first family in a periodic table with the Group 1 elements (だいいちぞくげんそ). Hydrogen・Lithium・Sodium・Potassium・Rubidium・Cesium・FranciumBut, I correspond to this. Of these, I say alkali metals (alkali metals) about the element except hydrogen and show a metallic property because most integumentary covering s orbital electron behaves as a free electron in the simple substance.
In element group located the left side most of the periodic table, the valence electron is an electron in the s orbit of the most integumentary covering. Only 1 electron occupies the s orbit.
Table of contents
Alkali metals
In Group 1 elements, a name given about a common part of the elemental chemical property to have is an alkali metal. In other words, a complete commonality does not exist even if it is the element of the same family because a family of the periodic table is the division which paid its attention to a commonality of the electronic structure (even an other elements group is similar). Covalency is strong so that a period is small in the simple substance of the representative element, and a metal associativity is strong so that a period is big. I do the way of appearing in that only hydrogen shows covalency as for the property in the Group 1 elements, and the others show a metal associativity these representative elements [1].
Because elemental most to belong to Group 1 elements belonged to "alkali metals" which were a classification based on the chemical property, it has been performed for a long time considerably historically that I expressed Group 1 elements in other words with alkali metals. Therefore I am often considered equal to Group 1 elements and alkali metals in a wide sense. However, the viewpoint of the classification is difference in electronic structure or is not equal closely with the division of Group 1 elements and the division of alkali metals because there is whether it is quality of representative chemical commonality difference. However, common chemical property and a physical property exist with hydrogen and alkali metals and are not to be a different group at all.
Property
Lithium, sodium, potassium, rubidium, cesium of Group 1 elements except hydrogen are called an alkali metallic element, and a property resembles closely very much. On the other hand, hydrogen is remarkably different from the alkali metallic element in a property. In addition, lithium reacts with direct nitrogen and has the property different from other alkali metallic elements in some properties of matter [2].
The difference between hydrogen and other alkali metallic elements is caused by having closed shell structure or not of the electron configuration. When a monovalent positive ion is formed, in the case of an alkali metallic element, I am stabilized by contribution of the closed shell structure very much. On the other hand, ionization energy to separate an electron from a nucleus is very big, and there is not closed shell structure, and contribution of the stabilization does not exist because the proton which is a positive ion of hydrogen is a bare positive charge. Difference in behavior of such s electron gives covalency to hydrogen and gives an alkali metallic element a gold attribute.
On the other hand, the difference between lithium and other alkali metallic elements is caused by an ion radius of lithium. Because lithium has a small ion radius, electric charge / ion radius ratio is remarkably bigger than other alkali metallic elements. Therefore indicating the property similar to the Mg2+ which is alkaline earth metals element of big 2 values of electric charge / ion radius ratio rather than a univalent alkali metals ion in the property of reactivity and the compound equally [2]. For example, lithium reacts with nitrogen like magnesium directly and forms nitride, but other alkali metallic elements do not react for nitrogen. In addition, sulfate of lithium does not form alum whereas sulfate of other alkali metals forms alum [3].
A work function makes the Group 1 elements small, and there is characteristic that it has a big zirconium.
| Hydrogen 1H | Lithium 3Li | Sodium 11Na | Potassium 19K | Rubidium 37Rb | Cesium 55Cs | Francium 87Fr | |
|---|---|---|---|---|---|---|---|
| Electron configuration | 1s1 | [He] 2s1 | [Ne] 3s1 | [Ar] 4s1 | [Kr] 5s1 | [Xe] 6s1 | [Rn] 7s1 |
| The first ionization energy (kJ·mol-1) | 1312 | 513.3 | 495.8 | 418.8 | 403.0 | 375.7 | 392.8 |
| Electronic addition enthalpy (kJ·mol-1) | − | − | − | − | 46.88 | 45.51 | − |
| Electron affinity (kJ·mol-1) | 72.77 | 59.63 | 52.87 | − | − | − | − |
| Electronegativity (Allred-Rochow) | 2.20 | 0.97 | 1.01 | 0.91 | 0.89 | 0.86 | − |
| Ion radius (pm, M+) | −4 (I coordinate 2) | 73 (I coordinate 4) 90 (I coordinate 6) | 113 (I coordinate 4) 116 (I coordinate 6) | 152 (I coordinate 6) 165 (I coordinate 8) | 166 (I coordinate 6) 175 (I coordinate 8) | 181 (I coordinate 6) 202 (I coordinate 12) | − |
| Covalent radius (pm) | 37 | 134 | 154 | 196 | 211 | 225 | 260 |
| van der Waals radius (pm) | 120 | 182 | 227 | 275 | 244 | 343 | 348 |
| Melting point (K) | 14.025 | 453.69 | 370.87 | 336.53 | 312.46 | 301.59 | 300 |
| The boiling point (K) | 20.268 | 1615 | 1156 | 1032 | 961 | 944 | 950 |
| Reduction potential E0 (V, M+/M) | 0 | −3.040 | −2.713 | −2.929 | −2.924 | −2.923 | − |
In the following, I speak the property of alkali metals mainly. I speak the property of hydrogen with article hydrogen in detail.
Simple substance metal
The melting point is relatively low, and alkali metals are metal light relatively softly. In Li, Na, K, specific gravity is saved in water in 1 or less. Because crystal energy (dissociation enthalpy) decreases so that the reactivity is high, and the period of the periodic table grows all big, a tendency to react intensely is seen. I can produce it to get simple substance metal of lithium and sodium because (in other words, it is hard to be returned very much) that each these oxidation-reduction potential is very low electrolyzes fusion salt [4]. Potassium chloride which let melt potassium is made with sodium steam and a thing reacting without being suitable for production by the simple electrolysis because potassium, rubidium, cesium are easy to also vaporize a low melting point (H2O is broken down when is a water solution, and hydrogen is generated), and is provided by letting return each hydroxide to rubidium and cesium by metal magnesium and metal calcium [5]; [6]. With the Downs' method to get metal sodium by adding calcium chloride to molten sodium chloride as melting point depressant for the representative industrial production method, and electrolyzing it [7]. Besides, the strong reduction characteristics of this alkali metallic element are used for the Birch reduction (Bürch reduction) in the field of the organic chemistry.
Because both alkali metallic element simple substances react with water or atmospheric oxygen, it is saved in mineral oil in order to avoid them. It is necessary for the handling to consider it because it may self-ignite when I wipe oil and leave you unattended (three kinds of dangerous materials). The reactive height of alkali metals tends to be high as a big thing of the atomic weight, but only lithium generates nitriding lithium (Li3N) by a direct reaction about the reaction with nitrogen exceptionally [2].
The alkali metallic element in none indicating the flame reaction [8]. Because the light emission of sodium is monochromatic light of wavelength 589nm called the D string, it is used in a source of light to measure the optical rotation that I cannot measure when it is not monochromatic light [9]. Actually, this D string is twins line divided into two of them of D1 line of wavelength 589.592nm and the D2 line of wavelength 588.995nm not one line spectrum. As for this, for 2 the spin of the most integumentary covering electron of sodium; is because there is it, and, as for the spectrum of the alkali metallic element except sodium, it is by a similar reason in twins line [10]. Only cesium has to observe it in oxyhydrogen flame to get a high temperature necessary for excitation.
| Lithium | Sodium | Potassium | Rubidium | Cesium | Francium |
|---|---|---|---|---|---|
| Dark red | Yellow | Purple | 深赤色 | Violet | Unconfirmed |
In addition, francium is not produced from nature with a radioactive element, but it is confirmed I am composed in small quantities by nuclear reaction, and to have the properties of matter as alkali metals.
They utter hydrogen gas with the proton solvent including water and the alcohol and react, and the formed hydroxide or metal alkoxide are used as a strong base.
And the alkali metals ion forms various kinds of anion including the halogenous ion and water-soluble salt. This has a big contribution of alkali metals ion strongly hydrating. The solubility of these alkali metal salts is strongly influenced by the behavior of the alkali metals ion. For example, crown ether or the cryptand form alkali metals ion and a subsumption compound, and the salt is known to become soluble to an organic solvent.
A simple substance of alkali metals is all a crystal of the tesseral system of the body centered cubic lattice in the low temperature, but potassium, rubidium, cesium become the crystal of the tetragonal system in the normal temperature [11].
A work function makes use of a good point to be small, and the alloy based on alkali metals is used [12], and Sb-K-Cs alloy called vial Cali is used for the photoelectric aspect materials of the photomultiplier tube with the thing used in Super-Kamiokande [13].
Compound
Hydride
Alkali metals form univalent hydride expressed in general formula MH by heating alkali metals under a hydrogen current of air under a dry condition, but it is unstable [14] and I receive hydrolysis and dismantle these to hydroxide and hydrogen corresponding to original hydride except lithium hydride [15]. These hydride is ion type hydride taking sodium chloride type structure [15] and, as a hydride donor, are used as a base and a reducing agent. In addition, the 3 yuan compounds such as sodium borohydride or lithium aluminum hydride are formed, too [15].
Oxide
Alkali metals form oxide expressed in general formula M2O. The section of the alkali metals simple substance is covered to (partly hydroxide) including oxide immediately to react with atmospheric oxygen directly although I show metallic luster just after that and loses luster.
In addition, when it burns it in the air, it produces oxide with lithium mainly, but it forms metal peroxide expressed in general formula M2O2, and it is known for sodium mainly to form metal hyperoxide expressed in the case of the element in potassium periods more than it in general formula MO2. The big positive ion of the ion radius can stabilize a big anion making a pair by a lattice energy effect, and this is because I can form an even unstable peroxide ion and hyperoxide ion and a stable compound [16]. It is necessary to react it with hydrogen peroxide to form lithium peroxide [17], and a condition of the elevated temperature and pressure is necessary to form super sodium oxide [18]. All the hyperoxide of the alkali metallic element is paramagnetic substance and take crooked sodium chloride type structure [18]. In addition, ozonide is formed by the hydroxide of alkali metals and a reaction with the ozone [19]. The stability of this ozonide is also proportional to the size of the ion radius of the positive ion making a pair [20].
Because electronegativity is low, and alkali metals are very positive electrically, oxide reacts with water with fever intensely and generates hydroxide and the peroxide hydrolyzes it intensely and produces hydrogen peroxide or oxygen and I gradually dismantle the hyperoxide in the water solutions and produce oxygen [16].
Refer to an item of each oxygen, oxide for the general property of oxide not to limit to alkali metals.
Hydroxide
Alkali metals form hydroxide expressed in general formula MOH. It is the colorless crystal which is a low melting point and sublimates at 400 degrees Celsius from 350 degrees Celsius of the neighborhood of melting point [21]. It dissolves all in water and alcohol having deliquescence characteristics except lithium hydroxide easily while running a fever [22]. Indicating the basicity that is very strong because approximately completely ionize to alkali metals ion and a hydroxyl ion with the water solution of the hydroxide of alkali metals [23]. I form a dimer expressed in (MOH)2 in the gas state, and, as for the basic strength in the gas state, basicity becomes strong so that the atomic weight of alkali metals grows big, but the strength of the basicity in the solution is not this limit to be affected by solvent effects [24]. In addition, having very strong causticity, even platinum erodes in the fusion state [22]. I take in atmospheric carbon dioxide and am easy to form carbonate [25], and the commercial hydroxide slightly includes carbonate. For example, it is provided that a content of carbonate must be less than 1.0% with sodium hydroxide and potassium hydroxide of the reagent in Japanese Industrial Standards [26].
The hydroxide of carbonate of electrolysis and alkali metals of chloride of alkali metals which the hydroxide of alkali metals is equivalent to industrially or sulfate and alkaline earth metals double; is provided by letting dismantle it [27]. The former electrolysis method is rubidium and cesium, and the latter double decomposition method is used with sodium and potassium mainly [28]. Sodium hydroxide is a material very important industrially used for cheap alkali source et al. various uses in hydroxide of alkali metals, and the quantity of 902,178 tons a year is used in Japan in 2010 [29].
Halide
Generally, the halide of alkali metals is a solid at normal temperature; lithium fluoride (as for LiF, the solubility for 100 g of water 0.27 g of (18 degrees Celsius)) [30]や sodium fluoride (as for NaF, the solubility for 100 g of water 4 g of (0 degrees Celsius)) [31]The などの exception is the salt which is high in almost all solution although there is it. Factors to greatly participate in solution of the salt include the loss and gain of the income and expenditure with the energy lost with energy and cutting of the ion crystal lattice to be provided by the hydration of the alkali metals ion so that it is spoken by the above (they know a lot about article solution, dissolution). By what the hydration energy when a crystal of the lithium fluoride dissolves in the crystal lattice of the lithium fluoride about solution of the lithium fluoride being low (at 25 degrees Celsius 0.13 g/100 mL) because an ion radius is small at the same level in both fluoride ion (F-) and lithium ion (Li+) while it is from combination strong small, and an ion receives hydration does not deny by the lattice energy of the big thing [32].
| Material | Lattice energy | Hydration enthalpy change | Dissolution enthalpy change | Dissolution entropy change | Dissolution plaster cast free energy change |
|---|---|---|---|---|---|
| Lithium fluoride | 1046.4 kJ mol-1 | −1041.5 kJ mol-1 | 4.8 kJ mol-1 | −36.1 J mol-1K-1 | 15.6 kJ mol-1 |
With the thing indicating the basicity that pH of the water solution of the halide of alkali metals is often almost the neutrality, but is feeble in fluoride and iodide (e.g.,: with saturation NaF water solution pH 7.4). Hydrogen fluoride is weak acid, and this depends on a fluoride ion being slightly hydrolyzed, an iodide ion being easy to be oxidized again although the hydrogen iodide is strong acid, and a pole changing into hypoiodite. The thermal stability of the halide of alkali metals is stable so that atomic number on the alkali metals side is big, and it is stable so that atomic number on the halogen side is small again [33].
In a series of halide, an existing thing is sodium chloride most widely on the earth (NaCl).
Structure
Each halide of the alkali metallic element takes a simple tesseral system [34]. Halide of lithium, sodium, potassium and rubidium usually takes the face-centered cube lattice that 6 is closest packing structure called "sodium chloride type structure" of coordinating it, and halogenation cesium except fluorinated cesium takes the body centered cubic lattice which is not closest packing structure called "cesium chloride type structure" of 8 coordination [35]. However, it is known that rubidium chloride forms cesium chloride type structure at the low temperature with precedence [36], and cesium chloride does phase transition to sodium chloride type structure at 445 degrees Celsius again [30]. The difference in structure of such a halide depends on an alkali metallic element and the ion radius ratio of the halide ion, and a change of the structure happens after ion radius ratio (r+/r-) 0.72 [37]. It comes from the property that a crystal ion stabilizes by many coordination numbers and a positive ion and the high filling rate between anions, and clogged up in (the ion radius of the positive ion is small) that a positive ion and the anionic ion radius ratio are small and the coordination number that there is few it from the theory calculation by the rigid body ball approximation thickly is stable, and this is because the which does not take the closest packing in (the ion radius of the positive ion is big) that a positive ion and the anionic ion radius ratio are big and the coordination number that there is many it becomes stable [38].
Alloy
Alkali metals form amalgam in response to mercury [39]. Amalgam of sodium is used in technique to be called mercurial law to prepare high-purity sodium hydroxide [40]. In addition, it is used for the electrode reactions of alkali metals which I cannot use a normal electrode for as a sodium amalgam electrode [41]. There are a solid, a property to become the liquid if I reduce it if I increase ratios of sodium, and sodium amalgam is used as a strong reducing agent [39].
リチウム以外のアルカリ金属元素は、溶融させることでそれぞれ任意の割合で混合して合金を与えるが、リチウムはナトリウムとは380°C以上の条件で合金を作ることができるものの、それ以外のアルカリ金属元素とは合金を作ることができない[2]。アルカリ金属同士の合金で重要なものはナトリウムカリウム合金であり、カリウム含有率77.2 %のもので融点が-12.3°Cと常温で液体な低融点合金である[5]。その高い比熱によって核反応における熱媒体としての利用が検討されていたが、より安全な溶融ナトリウムへと移りこの用途では現在用いられていない[5]。また、モル濃度で41%のセシウム、47%のカリウム、12%のナトリウムからなる合金は、すべての合金の中で最低の融点 (−78 °C) を持つ[42][43]
註・出典
- ^ 水素も「超高圧下では高温でも固体となり、金属的な物性を示す」と理論的には示されているように、金属であるか非金属であるかは、元素の性質だけでなく物質の構造にも依存する。
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- ^ a b コットン、ウィルキンソン (1987) 253頁。
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- ^ Kaner, Richard (2003年). "C&EN: It's Elemental: The Periodic Table – Cesium". American Chemical Society. 2010年2月25日閲覧。
- ^ Taova, T. M. et al. (2003年6月22日). "Density of melts of alkali metals and their Na-K-Cs and Na-K-Rb ternary systems (PDF)". Fifteenth symposium on thermophysical properties, Boulder, CO, USA. 2010年9月26日閲覧。
参考文献
- F.A. コットン, G. ウィルキンソン 『コットン・ウィルキンソン無機化学（上）』 中原 勝儼、培風館、1987年、原書第4版。ISBN 4563041920。
- 足立吟也、岩倉千秋、馬場 章夫 『新しい工業化学-環境との調和をめざして』、2004年。ISBN 4759809554。
- 小出直之 『ビギナーズ化学』 化学同人、2003年。ISBN 4759808779。
- 櫻井武、鈴木晋一郎、中尾安男 『ベーシック無機化学』 化学同人、2003年。ISBN 4759809031。
- 千谷利三 『新版 無機化学（上巻）』 産業図書、1959年。
- C.F.ベル、K.A.K.ロット 『ベル・ロット無機化学-その現代的理解のために』 東京化学同人、1968年、第2版。
- P.Y.ブルース 『ブルース有機化学（上）』 大船泰史ほか、化学同人、2009年、第5版。ISBN 4759811680。
関連項目
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