Bromine (Br)
halogenLiquid
प्रमाणित अणुभार
79.904 u [७९.९०१, ७९.९०७]इलेक्ट्रॉन संरूपण
[Ar] 4s2 3d10 4p5द्रवणांक
-7.2 °Cउत्कलनांक
58.8 °Cघनता
3102.8 kg/m³ऑक्सिडीकरण अवस्था
−1, +1, +2, +3, +4, +5, +7विद्युतऋणता (पॉलिंग)
2.96आयनीकरण ऊर्जा (पहिली)
11.81381 eVशोधाचे वर्ष
1825अणुत्रिज्या
115 pmतपशील
Bromine is a halogen, group 17 element, and the only nonmetal that is liquid near room temperature. Elemental bromine occurs as diatomic Br₂ and is a dense, volatile, strongly oxidizing substance. In nature bromine is found mainly as bromide ions in seawater, salt lakes, and subsurface brines. Its chemistry is intermediate between chlorine and iodine, with important roles in flame retardants, drilling fluids, pharmaceuticals, and photographic chemistry.
Bromine is the only nonmetallic liquid element. It is a heavy, mobile, reddish-brown liquid, volatilizing readily at room temperature to a red vapor with a strong disagreeable odor, resembling chlorine, and having a very irritating effect on the eyes and throat; it is readily soluble in water or carbon disulfide, forming a red solution, is less active than chlorine but more so than iodine; it unites readily with many elements and has a bleaching action; when spilled on the skin it produces painful sores. It presents a serious health hazard, and maximum safety precautions should be taken when handling it.
The name derives from the Greek bromos for "bad stench" or "bad odour". It was first prepared by the German chemist Carl Löwig in 1825, but it was first publicly announced in 1826 by the French chemist and pharmacist Antoine-Jérôme Balard, and so the discovery is, therefore, credited to him.
The only nonmetallic element that is a liquid at normal room temperatures, bromine was produced by Carl Löwig, a young chemistry student, the summer before starting his freshman year at Heidelberg. When he showed his professor, Leopold Gmelin, the red, smelly liquid he had produced, Gmelin realized that this was an unknown substance and encouraged Löwig to produce more of it so they could study it in detail. Unfortunately, winter exams and the holidays delayed Löwig's work long enough for another chemist, Antoine-Jérôme Balard, to publish a paper in 1826 describing the new element. Balard was credited with the discovery and named it after the greek word for stench, bromos. Today, bromine is primarily obtained by treating brines from wells in Michigan and Arkansas with chlorine.
From the Greek word bromos, stench. Discovered by Balard in 1826, but not prepared in quantity until 1860.
Pure bromine is a dark red-brown, mobile liquid at ordinary conditions. It gives off a heavy red-brown vapor with a sharp, irritating odor. It freezes to a reddish solid and boils just above room temperature, so noticeable vapor is present from an open container.
Bromine compounds are used in flame retardants for plastics, textiles, and electronic materials, although some older persistent formulations have been restricted or replaced. Dense calcium bromide (CaBr₂), sodium bromide (NaBr), and zinc bromide (ZnBr₂) brines are used in oil and gas drilling and completion fluids. Silver bromide (AgBr) remains important in traditional photographic films and papers. Organobromine intermediates are also used in pharmaceuticals, agrochemicals, dyes, and specialty chemicals.
Elemental bromine is a hazardous material. It causes severe burns when it comes in contact with the skin and its vapor irritates the eyes, nose and throat. Most of the bromine produced in the United States was used in the manufacture of ethylene dibromide(C2H4Br2), a chemical added to leaded gasolines that prevented the accumulation of lead compounds within the engine. With the discontinuation of leaded gasolines in favor of unleaded gasolines, the demand for bromine has been greatly reduced. Silver bromide (AgBr), a chemical used in photography, now accounts for the largest use of bromine. Other bromine compounds are used in fumigants, in flameproofing agents and in some compounds used to purify water. Tyrian purple, an expensive purple dye known to ancient civilizations, was produced from an organic bromine compound secreted from a sea mussel known as the murex.
Bromine is used in making fumigants, flameproofing agents, water purification compounds, dyes, medicines, sanitizers, inorganic bromides for photography, etc. Organic bromides are also important.
Isotopes in Earth/Planetary Science
Molecules, atoms, and ions of the stable isotopes of bromine possess slightly different physical and chemical properties, and they commonly will be fractionated during physical, chemical, and biological processes, giving rise to variations in isotopic abundances and in atomic weights. There are substantial variations in the isotopic abundances of bromine in natural terrestrial materials (Fig. IUPAC.35.1). These variations are useful in investigating the origin of substances and studying environmental, hydrological, and geological processes [13] M. W. Wieser, T. B. Coplen. Pure Appl Chem.83, 359 (2011)., [278] R. L. Stotler, S. K. Frape, O. Shouakar-Stash. Chem. Geol.274, 38 (2010).. 79Br has been used as a groundwater tracer (Fig. IUPAC.35.2). Introduction of a solution spiked with 79Br to groundwater and measurement of the change in the isotope-amount ratio n(79Br)/n(81Br) over time has been used to monitor tracer breakthrough and to calculate bromide travel time [279] M. D’Alessandro, G. Bidoglio, F. Mousty, J. V. Sala Benito, A. Y. De Llano. J. Hydrol.193, 351 (1997)..
Isotopes in Medicine
77Br (with a half-life of 57 h) is used to label radiopharmaceuticals that bind to estrogen receptors for tumor imaging. 75Br (with a half-life of 97 min) is being used with positron emission tomography (PET) imaging [281] K. D. McElvany, J. A. Katzenellenbogen, K. E. Shafer, B. A. Siegel, S. G. Senderoff, M. J. Welch, Los Alamos Medical Radioisotope Group. J. Nucl. Med.23, 425 (1982)..
Isotopes Used as a Source of Radioactive Isotope(s)
79Br is used in the proton cyclotron to produce 77Kr, which decays to 77Br via the reaction 79Br (p, 3n) 77Kr, which decays into 77Br [282] E. Galiano, R. Tilbury. Appl. Radiat. Isot.49, 105 (1998)..
Bromine commonly forms bromide salts containing Br⁻, including sodium bromide (NaBr) and potassium bromide (KBr). It shows positive oxidation states in interhalogen and oxyanion chemistry, such as bromine chloride (BrCl), hypobromous acid (HOBr), bromate (BrO₃⁻), and perbromate (BrO₄⁻), though the higher oxidation states are less stable than comparable chlorine species. Hydrogen bromide (HBr) is a strong acid in water. Many organobromine compounds are useful synthetic intermediates because carbon-bromine bonds are reactive toward substitution and coupling reactions.
See more information at the Bromine compound page.
Elemental bromine (Br₂) is highly corrosive, toxic by inhalation, and a severe irritant to skin, eyes, and mucous membranes. Its vapor is hazardous even at low concentrations and reacts with many organic materials and reducing agents. Concentrated hydrobromic acid (HBr) is strongly acidic and corrosive. Some organobromine compounds are persistent, bioaccumulative, or toxic, but hazards vary widely with structure and exposure route.
Bromide is a natural constituent of seawater and evaporite brines, and it is cycled through oceans, salt deposits, aerosols, and biological processes. Marine organisms produce many organobromine compounds, some of which enter atmospheric chemistry. In water treatment, bromide can be oxidized to reactive bromine species and brominated disinfection by-products. Persistent brominated flame retardants can accumulate in sediments and biota, depending on their structure and use history.
Commercial bromine is produced mainly by oxidizing bromide-rich brines and stripping the liberated bromine from solution. Major feedstocks include highly saline inland brines, salt-lake brines, and some subsurface brines associated with mineral or hydrocarbon production. Demand is tied to flame retardants, drilling fluids, water-treatment chemicals, and specialty synthesis. Supply is geographically concentrated where suitable brines are available, and recycling is limited for many dispersive uses, although some brominated materials and process streams can be recovered or managed in closed systems.
A member of the halogen group, bromine is obtained from natural brines from wells in Michigan and Arkansas. Some bromine is extracted today from seawater, which contains only about 85 ppm.
Bromine is a relatively scarce element in the cosmos compared with lighter halogens. It is produced by neutron-capture processes in earlier generations of stars and is incorporated into dust, meteorites, and planetary materials in small amounts. On Earth and other volatile-bearing bodies, its geochemistry is controlled mainly by the soluble bromide ion, which concentrates in brines during evaporation.
- Bromine is one of only two elements that are liquid at standard laboratory temperatures; the other is mercury.
- Its name comes from a Greek word referring to stench, reflecting the odor of Br₂ vapor.
- Silver bromide darkens on exposure to light, a property central to photographic emulsions.
- Bromide ions are usually more concentrated in late-stage evaporite brines than in ordinary seawater.
- Elemental bromine is dense enough that many common solids float on it, but contact is dangerous.
प्रतिमा
गुणधर्म
भौतिक
- अणुत्रिज्या (अनुभवाधारित)
- 115 pm सर्व घटकांच्या अणुत्रिज्या (अनुभवाधारित) ची तुलना करा →
- सहसंयुजी त्रिज्या
- 120 pm सर्व घटकांच्या सहसंयुजी त्रिज्या ची तुलना करा →
- व्हॅन डर वाल्स त्रिज्या
- 183 pm सर्व घटकांच्या व्हॅन डर वाल्स त्रिज्या ची तुलना करा →
- घनता
- 3102.8 kg/m³ सर्व घटकांच्या घनता ची तुलना करा →
- मोलर आयतन
- 0.0235 L/mol
- STP येथे अवस्था
- द्रव सर्व घटकांच्या STP येथे अवस्था ची तुलना करा →
- द्रवणांक
- -7.2 °C सर्व घटकांच्या द्रवणांक ची तुलना करा →
- उत्कलनांक
- 58.8 °C सर्व घटकांच्या उत्कलनांक ची तुलना करा →
- उष्णता चालकता
- 0.005 W/(m·K) सर्व घटकांच्या उष्णता चालकता ची तुलना करा →
- विशिष्ट उष्माधारकता
- 0.474 J/(g·K) सर्व घटकांच्या विशिष्ट उष्माधारकता ची तुलना करा →
- मोलर उष्माधारकता
- 75.69 J/(mol·K) सर्व घटकांच्या मोलर उष्माधारकता ची तुलना करा →
- स्फटिक संरचना
- लंबसमचतुर्भुजी सर्व घटकांच्या स्फटिक संरचना ची तुलना करा →
रासायनिक
- विद्युतऋणता (पॉलिंग)
- 2.96 सर्व घटकांच्या विद्युतऋणता (पॉलिंग) ची तुलना करा →
- विद्युतऋणता (ॲलन)
- 2.685
- इलेक्ट्रॉन आसक्ती
- 3.3635 eV
- आयनीकरण ऊर्जा (पहिली)
- 11.81381 eV सर्व घटकांच्या आयनीकरण ऊर्जा (पहिली) ची तुलना करा →
- आयनीकरण ऊर्जा (दुसरी)
- 21.591074 eV सर्व घटकांच्या आयनीकरण ऊर्जा (दुसरी) ची तुलना करा →
- आयनीकरण ऊर्जा (तिसरी)
- 34.87112 eV सर्व घटकांच्या आयनीकरण ऊर्जा (तिसरी) ची तुलना करा →
- आयनीकरण ऊर्जा (चौथी)
- 47.782164 eV सर्व घटकांच्या आयनीकरण ऊर्जा (चौथी) ची तुलना करा →
- आयनीकरण ऊर्जा (पाचवी)
- 59.595205 eV सर्व घटकांच्या आयनीकरण ऊर्जा (पाचवी) ची तुलना करा →
- ऑक्सिडीकरण अवस्था
- −1, +1, +2, +3, +4, +5, +7 सर्व घटकांच्या ऑक्सिडीकरण अवस्था ची तुलना करा →
- संयुजा इलेक्ट्रॉन
- 7 सर्व घटकांच्या संयुजा इलेक्ट्रॉन ची तुलना करा →
- इलेक्ट्रॉन संरूपण
- [Ar] 4s2 3d10 4p5
उष्मागतिक
- त्रिक बिंदू (तापमान)
- -7.25 °C
- त्रिक बिंदू (दाब)
- 5879 Pa
- क्रांतिक बिंदू (तापमान)
- 315 °C
- क्रांतिक बिंदू (दाब)
- 1.034e+7 Pa
- द्रवण उष्मा
- 0.10955071 eV सर्व घटकांच्या द्रवण उष्मा ची तुलना करा →
- बाष्पीभवन उष्मा
- 0.31051459 eV सर्व घटकांच्या बाष्पीभवन उष्मा ची तुलना करा →
- अणूकरण उष्मा
- 1.159766 eV
- अणूकरण एन्थाल्पी
- 1.159248 eV
केंद्रकीय
- प्रोटॉन
- 35 सर्व घटकांच्या प्रोटॉन ची तुलना करा →
- न्यूट्रॉन
- 44 सर्व घटकांच्या न्यूट्रॉन ची तुलना करा →
- ज्ञात समस्थानिके
- 34 सर्व घटकांच्या ज्ञात समस्थानिके ची तुलना करा →
- स्थिर समस्थानिके
- 2 सर्व घटकांच्या स्थिर समस्थानिके ची तुलना करा →
- सर्वाधिक स्थिर समस्थानिक
- Br-79
- शोधाचे वर्ष
- 1825
विपुलता
- विपुलता (पृथ्वीचे कवच)
- 2.4 mg/kg सर्व घटकांच्या विपुलता (पृथ्वीचे कवच) ची तुलना करा →
- विपुलता (महासागर)
- 67.3 mg/L सर्व घटकांच्या विपुलता (महासागर) ची तुलना करा →
स्फटिक संरचना
- जालक स्थिरांक a
- 667 pm
इलेक्ट्रॉन संरचना
- प्रत्येक कवचातील इलेक्ट्रॉन
- 2, 8, 18, 7 सर्व घटकांच्या प्रत्येक कवचातील इलेक्ट्रॉन ची तुलना करा →
ओळखचिन्हे
- CAS क्रमांक
- 7726-95-6 सर्व घटकांच्या CAS क्रमांक ची तुलना करा →
- टर्म चिन्ह
- 2P°3/2
- InChI
- InChI=1S/Br
- InChI की
- WKBOTKDWSSQWDR-UHFFFAOYSA-N
इलेक्ट्रॉन संरूपण मोजलेले
Br: 3d¹⁰ 4s² 4p⁵[Ar] 3d¹⁰ 4s² 4p⁵1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁵अणुप्रतिमान
समस्थानिकांमुळे न्यूट्रॉन संख्या, वस्तुमान आणि स्थैर्य बदलते — विद्युतदृष्ट्या उदासीन अणूचे इलेक्ट्रॉन संरूपण बदलत नाही.
योजनात्मक अणुप्रतिमान, प्रमाणानुसार नाही.
अणूची विशिष्ट ओळख
उत्सर्जन / शोषण वर्णपट
समस्थानिक वितरण
| वस्तुमानांक | अणुवस्तुमान (u) | नैसर्गिक विपुलता | अर्धायुष्य |
|---|---|---|---|
| 79 स्थिर | ७८.९१८३३७६ ± ०.०००००१४ | 50.6900% | स्थिर |
| 81 स्थिर | ८०.९१६२८९७ ± ०.०००००१४ | 49.3100% | स्थिर |
अवस्था / स्थिती
कारण: द्रवणांक (-7.2 °C) आणि उत्कलनांक (58.8 °C) यांच्या दरम्यान
योजनात्मक, प्रमाणानुसार नाही
अवस्थांतर बिंदू
अवस्थांतर ऊर्जा
द्रवणांकावर 1 mol वितळवण्यासाठी आवश्यक ऊर्जा
उत्कलनांकावर 1 mol चे बाष्पीभवन करण्यासाठी आवश्यक ऊर्जा
घनता
प्रमाणित परिस्थितीत
द्रव अवस्थेसाठी उपलब्ध नाही
प्रगत
अणुवर्णपट
35 पैकी 10 दाखवले आहेत. आयनाच्या विद्युतभारानुसार चढत्या क्रमाने मांडलेले.
वर्णरेषांचा संग्रह ?
| आयन | विद्युतभार | एकूण वर्णरेषा | संक्रमण संभाव्यता | पातळ्यांची नामांकने |
|---|---|---|---|---|
| Br I | 0 | 170 | 54 | 170 |
| Br II | +1 | 118 | 3 | 0 |
| Br III | +2 | 75 | 0 | 0 |
| Br IV | +3 | 136 | 0 | 136 |
| Br V | +4 | 22 | 0 | 0 |
ऊर्जा पातळ्यांचा संग्रह ?
| आयन | विद्युतभार | पातळ्या |
|---|---|---|
| Br I | 0 | 265 |
| Br II | +1 | 132 |
| Br III | +2 | 53 |
| Br IV | +3 | 43 |
| Br V | +4 | 10 |
| Br VI | +5 | 12 |
| Br VII | +6 | 6 |
| Br VIII | +7 | 12 |
| Br IX | +8 | 5 |
| Br X | +9 | 2 |
आयनिक त्रिज्या
| विद्युतभार | समन्वय | प्रचक्रण | त्रिज्या |
|---|---|---|---|
| -1 | 6 | उपलब्ध नाही | 196 pm |
| +3 | 4 | उपलब्ध नाही | 59 pm |
| +5 | 3 | उपलब्ध नाही | 31 pm |
| +7 | 4 | उपलब्ध नाही | 25 pm |
| +7 | 6 | उपलब्ध नाही | 39 pm |
संयुगे
समस्थानिके (2)
| वस्तुमानांक | अणुवस्तुमान (u) | नैसर्गिक विपुलता | अर्धायुष्य | क्षय प्रकार | |
|---|---|---|---|---|---|
| 79 स्थिर | ७८.९१८३३७६ ± ०.०००००१४ | 50.6900% ± 0.0700% | स्थिर | stable | |
| 81 स्थिर | ८०.९१६२८९७ ± ०.०००००१४ | 49.3100% ± 0.0700% | स्थिर | stable |
विस्तारित गुणधर्म
सहसंयुजी त्रिज्या (विस्तारित)
- सहसंयुजी त्रिज्या (प्युक्को)
- 114 pm
- सहसंयुजी त्रिज्या (प्युक्को, दुहेरी बंध)
- 109 pm
- सहसंयुजी त्रिज्या (प्युक्को, तिहेरी बंध)
- 110 pm
- सहसंयुजी त्रिज्या (ब्रॅग)
- 119 pm
व्हॅन डर वाल्स त्रिज्या
- Bondi
- 183 pm
- Batsanov
- 190 pm
- Alvarez
- 186 pm
- UFF
- 418.9 pm
- MM3
- 222 pm
- Dreiding
- 395 pm
- Rowland–Taylor
- 187 pm
अणुत्रिज्या आणि धात्विक त्रिज्या
- अणुत्रिज्या (राह्म)
- 219 pm
- धात्विक त्रिज्या (C12)
- 117 pm
क्रमांकन मापनपट्ट्या
- Mendeleev
- 108
- Pettifor
- 98
- Glawe
- 100
विद्युतऋणता मापनपट्ट्या
- Ghosh
- 0
- Gunnarsson–Lundqvist
- 8
- Robles–Bartolotti
- 7
ध्रुवणक्षमता आणि अपस्करण
- द्विध्रुव ध्रुवणक्षमता
- 21 a.u.
- द्विध्रुव ध्रुवणक्षमता (अनिश्चितता)
- 1 a.u.
- C₆
- 162 Ha·Bohr6
- C₆ (Gould–Bučko)
- 187 Ha·Bohr6
रासायनिक आसक्ती
- प्रोटॉन आसक्ती
- 554.4 kJ/mol
- वायूची क्षारकता
- 531.2 kJ/mol
पुरवठा जोखीम आणि अर्थकारण
- उत्पादनाचे केंद्रीकरण
- 44
- सापेक्ष पुरवठा जोखीम
- 7
- साठ्यांचे वितरण
- 64
- राजकीय स्थैर्य (प्रमुख उत्पादक)
- 57
- राजकीय स्थैर्य (सर्वाधिक साठे असलेला देश)
- 57
अवस्थांतरे आणि अपरूपे
| द्रवणांक | 265.95 K |
| उत्कलनांक | 331.95 K |
| क्रांतिक बिंदू (तापमान) | 588.15 K |
| क्रांतिक बिंदू (दाब) | 10.34 MPa |
| त्रिक बिंदू (तापमान) | 265.9 K |
| त्रिक बिंदू (दाब) | 5.88 kPa |
ऑक्सिडीकरण अवस्थांचे वर्ग
प्रगत संदर्भ माहिती
परिरक्षण स्थिरांक (8)
| n | कक्षिका | σ |
|---|---|---|
| 1 | s | 0.7529 |
| 2 | p | 3.9436 |
| 2 | s | 9.3566 |
| 3 | d | 15.4409 |
| 3 | p | 15.4292 |
| 3 | s | 14.7815 |
| 4 | p | 25.972 |
| 4 | s | 24.4472 |
स्फटिक त्रिज्यांचा तपशील (5)
| विद्युतभार | CN | प्रचक्रण | rcrystal (pm) | उत्पत्ती |
|---|---|---|---|---|
| -1 | VI | 182 | Pauling's (1960) crystal radius, | |
| 3 | IVSQ | 73 | ||
| 5 | IIIPY | 45 | ||
| 7 | IV | 39 | ||
| 7 | VI | 53 | Ahrens (1952) ionic radius, |
समस्थानिक क्षय प्रकार (54)
| समस्थानिक | मोड | तीव्रता |
|---|---|---|
| 65 | p | — |
| 66 | p | — |
| 67 | p | — |
| 68 | p | — |
| 69 | p | 100% |
| 70 | B+ | 100% |
| 70 | B+p | — |
| 71 | B+ | 100% |
| 72 | B+ | 100% |
| 73 | B+ | 100% |
क्ष-किरण प्रकीर्णन गुणक (506)
| ऊर्जा (eV) | f₁ | f₂ |
|---|---|---|
| 10 | — | 5.16199 |
| 10.1617 | — | 5.31855 |
| 10.3261 | — | 5.47986 |
| 10.4931 | — | 5.64606 |
| 10.6628 | — | 5.8173 |
| 10.8353 | — | 5.99373 |
| 11.0106 | — | 6.17552 |
| 11.1886 | — | 6.36281 |
| 11.3696 | — | 6.5558 |
| 11.5535 | — | 6.75463 |
अतिरिक्त माहिती
Estimated Crustal Abundance
The estimated element abundance in the earth's crust.
2.4 milligrams per kilogram
संदर्भ (1)
Estimated Oceanic Abundance
The estimated element abundance in the earth's oceans.
6.73×101 milligrams per liter
संदर्भ (1)
Sources
Sources of this element.
A member of the halogen group, bromine is obtained from natural brines from wells in Michigan and Arkansas. Some bromine is extracted today from seawater, which contains only about 85 ppm.
संदर्भ (1)
- [6] Bromine https://periodic.lanl.gov/35.shtml
Production
Production of this element (from raw materials or other compounds containing the element).
Much of the bromine output in the U.S. was used in the production of ethylene dibromide, a lead scavenger used in making gasoline anti-knock compounds. Lead in gasoline, however, has been drastically reduced due to environmental considerations. This will greatly affect future production of bromine.
संदर्भ (1)
- [6] Bromine https://periodic.lanl.gov/35.shtml
संदर्भ
(9)
Data deposited in or computed by PubChem
The half-life and atomic mass data was provided by the Atomic Mass Data Center at the International Atomic Energy Agency.
Element data are cited from the Atomic weights of the elements (an IUPAC Technical Report). The IUPAC periodic table of elements can be found at https://iupac.org/what-we-do/periodic-table-of-elements/. Additional information can be found within IUPAC publication doi:10.1515/pac-2015-0703 Copyright © 2020 International Union of Pure and Applied Chemistry.
The information are cited from Pure Appl. Chem. 2018; 90(12): 1833-2092, https://doi.org/10.1515/pac-2015-0703.
Thomas Jefferson National Accelerator Facility (Jefferson Lab) is one of 17 national laboratories funded by the U.S. Department of Energy. The lab's primary mission is to conduct basic research of the atom's nucleus using the lab's unique particle accelerator, known as the Continuous Electron Beam Accelerator Facility (CEBAF). For more information visit https://www.jlab.org/
The periodic table at the LANL (Los Alamos National Laboratory) contains basic element information together with the history, source, properties, use, handling and more. The provenance data may be found from the link under the source name.
The periodic table contains NIST's critically-evaluated data on atomic properties of the elements. The provenance data that include data for atomic spectroscopy, X-ray and gamma ray, radiation dosimetry, nuclear physics, and condensed matter physics may be found from the link under the source name. Ref: https://www.nist.gov/pml/atomic-spectra-database
This section provides all form of data related to element Bromine.
The element property data was retrieved from publications.