หน้า 12
The Titanium and
Vanadium Groups
The titanium group of elements consists of titanium (Ti, element 22), zirconium (Zr, element 40), and hafnium (Hf, element 72). Th e
vanadium group consists of vanadium (V, element 23), niobium (Nb,
element 41), and tantalum (Ta, element 73).
Th e titanium metals are found in group IVA. Each of these elements is
tetravalent, meaning that its chemistry is dominated by the “+4” oxidation
state. Titanium is the best-known element in the group. Titanium oxide
(TiO
2) is a white paint pigment. Titanium alloys—such as those used
in golf clubs, surgical instruments, and prosthetics—are known for their
exceptional strength. Zircons are familiar diamond-like gems composed
of zirconium silicate, ZrSiO
4. Hafnium is probably less familiar to most
people, but it is an important component of control rods in the fuel assemblies of nuclear reactors and is important in the semiconductor industry.
หน้า 13
THE BASICS OF TITANIUM
Symbol: Ti
Atomic number: 22
Atomic mass: 47.867
Electronic confi guration: [Ar]4s23d2
T
melt = 3,034°F (1,668°C)
T
boil = 5,949°F (3,287°C)
Abundance in Earth’s crust = 6600 ppm
Isotope Z N Relative Abundance
46
22Ti 22 24 8.25%
47
22Ti 22 25 7.44%
48
22Ti 22 26 73.72%
49
22Ti 22 27 5.41%
50
22Ti 22 28 5.18%
THE BASICS OF ZIRCONIUM
Symbol: Zr
Atomic number: 40
Atomic mass: 91.224
Electronic confi guration: [Kr]5s24d2
T
melt = 3,371°F (1,855°C)
T
boil = 7,968°F (4,409°C)
Abundance in Earth’s crust = 130 ppm
Isotope Z N Relative Abundance
90
40Zr 40 50 51.45%
91
40Zr 40 51 11.22%
92
40Zr 40 52 17.15%
94
40Zr 40 54 17.38%
96
40Zr 40 56 2.80%
หน้า 14
THE BASICS OF HAFNIUM
Symbol: Hf
Atomic number: 72
Atomic mass: 178.49
Electronic confi guration:
[Xe]6s24f145d2
T
melt = 4,051°F (2,233°C)
T
boil = 8,317°F (4,603°C)
Abundance in Earth’s crust = 3.3 ppm
Isotope Z N Relative Abundance
174
72Hf 72 102 0.16%
176
72Hf 72 104 5.26%
177
72Hf 72 105 18.60%
178
72Hf 72 106 27.28%
179
72Hf 72 107 13.62%
180
72Hf 72 108 35.08%
Th e vanadium metals are found in group VA. Each of these ele
ments is pentavalent, meaning that the “+5” oxidation state is importan
to each. Vanadium, however, forms compounds that exhibit a relatively
large number of oxidation states. In addition to the “+5” state, there ar
the “+2,” “+3,” and “+4” states. Similarly, niobium exhibits a “+3” stat
in addition to the “+5”.
The asTroPhysics of The TiTanium grouP:
Ti, Zr, hf
Titanium 44, an α-process element, is synthesized in very large super
novae. Alpha-process elements are synthesized by sequential absorption
of alpha particles, which consist of four particles, so these elements al
have mass numbers that are multiples of four. Th e following reaction
synthesizes titanium 44 in the atmospheres of expanding supernovae
which distribute this radioactive isotope into the surrounding space.
40
20Ca + 4 2α → 44 22Ti
หน้า 15
Titanium 44 decays with a half-life of 59 days to 44Sc. Scandium 44
is itself unstable and decays with a half-life of 1.8 days via emission of a
photon with the energy of 1.156 million electron volts (MeV), producing the stable isotope 44Ca. This is the signature emission line in a stellar
spectrum that tells astronomers 44Ti was once present.
A curious stellar object is the so-called titanium star, Cas A, which
is a supernova remnant about 9,000 light years away with a neutron
star at its center. The blast should have been observable on Earth in the
mid-17th century, although there is no record of any such viewing. This
supernova is unique in that it produced an unprecedented excess of 44Ti
relative to 56Ni (which is produced in all supernovae). Since the synthesis of titanium requires temperatures on the order of 5 billion Kelvin, and gravitational contraction temperatures rise directly with the
mass of a star, the original star must have been an exceptionally massive
object before its demise.
The most abundant isotope of titanium on Earth—Ti-48, which is
stable—is not a product of stellar nucleosynthesis, but of the beta decay
of terrestrial scandium 48 or vanadium 48.
Like yttrium and most other elements heavier than iron, zirconium
and hafnium syntheses occur in stars via neutron capture onto lighter
elements. Zirconium abundance in stellar atmospheres presents some
surprises, however. Like yttrium, it appears to be deficient in stars with
low metal content, but the ratios of these two elements relative to iron
fluctuate from star to star, even when the stars are of similar types. However, there is less variability in abundances of these elements relative to
titanium, which is puzzling.
Another area of interest is the so-called zirconium conflict, which
refers to a confusing situation observed in some HgMn stars where the
spectral line corresponding to doubly ionized zirconium (Zr2+) is much
stronger than that belonging to the singly ionized atoms (Zr+). This is
counterintuitive, because more energy is required to remove two electrons than just one. A broadening of excitation energy levels within the
atom might, however, cause an atomic emission line to appear dimmer. One way this could happen is through bombardment of zirconium
atoms by free-flying electrons, of which huge numbers exist in the hot
gas of a star. This electron-impact broadening would have a greater
หน้า 16
influence on Zr+ than on Zr2+, but the calculated effect is not enough to
explain the observed differences.
The abovementioned anomalies indicate an incomplete scientific
understanding of the dynamic processes within stellar atmospheres and
interiors and the need for more observational data.
discovery and naming of TiTanium,
Zirconium, and hafnium
Titanium was discovered by the English clergyman, the Reverend William Gregor (1761–1817). A graduate of Cambridge University, Gregor
served several churches but spent most of his career as the rector at
a church in Creed, England, from 1793 until 1817. Gregor’s friend,
chemist John Warltire (1739–1810), introduced him to chemistry and
mineralogy. Gregor was particularly attracted to mineralogy and was
well known for his analyses of England’s minerals. Intrigued by a black
magnetic sand from his parish, he analyzed it and found it to be 46.56
percent magnetite (an iron oxide), 3.5 percent silica, 45 percent an
unknown reddish-brown substance, and 4.94 percent other material.
Gregor showed his results to another friend, John Hawkins. The
two men agreed that the reddish-brown substance was a mineral that
most likely contained a new element. Hawkins suggested naming the
new element menachanite after the Menachan Valley in which the sand
had been found. Gregor’s parish responsibilities prevented him from
pursuing the matter further. Unfortunately, he died of tuberculosis in
1817 without ever returning to his research.
Because of Gregor’s declining health, menachanite was all but forgotten. In 1795, however, the German chemist Martin Heinrich Klaproth (1743–1817) began investigating a specimen of the mineral rutile
(titanium oxide) from Hungary. From the rutile, he separated a metallic
oxide whose properties remarkably resembled the properties of menachanite. Klaproth began studying both minerals, carefully comparing
their properties, and concluded that they were the same metallic oxide.
Although he gave William Gregor full credit for priority of discovery,
Klaproth chose not to adopt Gregor’s name of menachanite for the new
element. Instead, deciding there were no special properties of the element or peculiarities regarding its origin, he chose a name that had
หน้า 17
nothing to do with the element’s properties. Klaproth chose the name
titanium after the Greek gods called the Titans, the children of Uranus
and Gaia.
A number of minerals contain zirconium. Zircon, a trace mineral
common to most granites, has been used as a gemstone since ancient
times. Until nearly 1800, however, all analyses of zirconium minerals
were erroneous. They were reported to contain silica, iron oxide, alumina, lime (calcium oxide), and other minerals, but nothing that would
have been a new element.
In 1789, Klaproth analyzed zircon and discovered that it contained
the mineral zirconia (later shown to be zirconium oxide, ZrO
2). In 1824,
Berzelius heated a sample of zirconia with potassium metal. Potassium
reduced the zirconium to an impure powdered form of the metal. During the next 90 years, chemists improved the process for isolating zirconium and gradually succeeded in obtaining samples of zirconium of
successively higher purity. In 1914, a completely pure sample of zirconium was finally obtained by reducing zirconium tetrachloride (ZrCl4)
with sodium. In the end, Klaproth was credited with zirconium’s discovery. The name zirconium itself was derived from the mineral zirconia.
In 1911, an element was discovered that was believed to be a lanthanide, which would have placed its atomic number between 57 and 71.
After World War I, this element was found to occur mostly in titanium
ores and to be more similar to zirconium than to the lanthanides. The
Danish physicist Niels Bohr (1885–1962) suggested that this unknown
element was more likely a transition metal in the titanium family. In
1923, acting upon Bohr’s suggestion, the Hungarian chemist George
Charles de Hevesy (1889–1966) and his coworker, the German physicist
Dirk Coster (1889–1950), used X-ray analysis to prove that the atomic
number of the unknown element had to be 72, which placed the element after the lanthanide series and below zirconium. Although neither
de Hevesy nor Coster was Danish, the two men decided to name element 72 hafnium, after Bohr’s home of Copenhagen, Denmark.
The chemisTry of The TiTanium grouP
Titanium is element 22, with a density of 4.5g/cm3. Titanium is a silverywhite metal that is lighter and stronger than steel and very corrosion
หน้า 12ไทเทเนียม และกลุ่มวาเนเดียมกลุ่มไทเทเนียมขององค์ประกอบของไททาเนียม (ตี้ องค์ประกอบ 22), เซอร์โคเนียม (Zr องค์ประกอบ 40), และแฮฟเนียม (Hf องค์ประกอบ 72) อี Thวาเนเดียมประกอบด้วยวาเนเดียม (V องค์ประกอบ 23), ไนโอเบียม (Nbองค์ประกอบ 41), และแทนทาลัม (Ta องค์ประกอบ 73)Th อีไทเทเนียมโลหะจะพบได้ในกลุ่มความ แต่ละองค์ประกอบเหล่านี้คือtetravalent หมายความ ว่า เคมีที่ถูกครอบงำ โดยออกซิเดชัน "+ 4"รัฐ ไทเทเนียมเป็นองค์ประกอบรู้จักในกลุ่ม ไทเทเนียมออกไซด์(TiO2) เป็นผงสีขาว โลหะผสมไทเทเนียม — เช่นใช้กอล์ฟ เครื่องมือผ่าตัด และ prosthetics — เป็นที่รู้จักสำหรับพวกเขาความแข็งแรงพิเศษ Zircons คุ้นเคยเช่นเพชรอัญมณีประกอบด้วยของเซอร์โคเนียมซิลิเก ZrSiO4. แฮฟเนียมเป็นคงไม่คุ้นเคยให้มากที่สุดคน แต่มันเป็นส่วนประกอบสำคัญของก้านควบคุมในแอสเซมบลีเชื้อเพลิงของเตาปฏิกรณ์นิวเคลียร์ และมีความสำคัญในอุตสาหกรรมสารกึ่งตัวนำหน้า 13พื้นฐานของไทเทเนียมสัญลักษณ์: ตี้เลขอะตอม: 22มวลอะตอม: 47.867Guration confi อิเล็กทรอนิกส์: [Ar] 4s23d2Tละลาย = 3,034° F (1,668° C)Tต้ม = 5,949° F (3,287° C)ความอุดมสมบูรณ์ในเปลือกโลก = 6600 ppmความสัมพันธ์ของ N ไอโซโทป Z4622Ti 22 24 8.25%4722Ti 22 25 7.44%4822Ti 22 26 73.72%4922Ti 22 27 5.41%5022Ti 22 28 5.18%พื้นฐานของเซอร์โคเนียมสัญลักษณ์: Zrเลขอะตอม: 40มวลอะตอม: 91.224Guration confi อิเล็กทรอนิกส์: [Kr] 5s24d2Tละลาย = 3,371° F (1,855° C)Tต้ม = 7,968° F (4,409° C)ความอุดมสมบูรณ์ในเปลือกโลก = 130 ppmความสัมพันธ์ของ N ไอโซโทป Z9040Zr 40 50 51.45%9140Zr 40 51 11.22%9240Zr 40 52 17.15 น.%9440Zr 40 54 17.38%9640Zr 40 56 2.80%หน้า 14พื้นฐานของแฮฟเนียมสัญลักษณ์: Hfเลขอะตอม: 72มวลอะตอม: 178.49Guration confi อิเล็กทรอนิกส์:[Xe] 6s24f145d2Tละลาย = 4,051° F (2,233° C)Tต้ม = 8,317° F (4,603° C)ความอุดมสมบูรณ์ในเปลือกโลก = 3.3 ppmความสัมพันธ์ของ N ไอโซโทป Z17472Hf 72 102 0.16%17672Hf 72 104 5.26%17772Hf 72 105 18.60%17872Hf 72 106 27.28%17972Hf 72 107 13.62%18072Hf 72 108 35.08%พบในกลุ่ม VA. Th อีวาเนเดียมโลหะ เอเลเหล่านี้แต่ละments เป็น pentavalent หมายความ ว่า สถานะออกซิเดชัน "+ 5" importanแต่ละ วาเนเดียม ไร แบบฟอร์มสารที่แสดงค่อนข้างจำนวนมากของอเมริกาเกิดออกซิเดชัน นอกจากรัฐ "+ 5", ar มี"+ 2 "+ 3" และ"+ 4"รัฐ ในทำนองเดียวกัน ไนโอเบียมจัดแสดงสถิติ "+ 3"นอกจากนี้ "+ 5"ฟิสิกส์ดาราศาสตร์ของไทเทเนียมกลุ่ม:ตี้ Zr, hfเป็นสังเคราะห์ไทเทเนียม 44 องค์ประกอบ กระบวนการด้วยกองทัพในซุปเปอร์ที่มีขนาดใหญ่มากnovae องค์ประกอบกระบวนการอัลฟาจะสังเคราะห์ โดยการดูดซึมตามลำดับของอนุภาค ซึ่งประกอบด้วยอนุภาค 4 ดังนั้นอัลองค์ประกอบเหล่านี้มีเลขมวลที่คูณสี่ Th อีต่อปฏิกิริยาsynthesizes ไทเทเนียม 44 ในบรรยากาศการขยาย supernovaeซึ่งกระจายไอโซโทปกัมมันตรังสีนี้ลงในพื้นที่โดยรอบ4020Ca + 4 2α → 44 22Tiหน้า 15Decays ไทเทเนียม 44 กับ half-life ของ 44Sc สแกนเดียม 44 59 วันตัวมันเองไม่เสถียรและ decays กับ half-life ของ 1.8 ผ่านไอเสียการโฟตอน มีพลังงานของ 1.156 ล้านอิเล็กตรอนโวลต์ (MeV), ผลิต 44Ca ไอโซโทปเสถียร เป็นลายเซ็นมลพิษบรรทัดเป็นดาวฤกษ์สเปกตรัมที่บอกดารา 44Ti ได้เมื่อมีวัตถุของดาวฤกษ์ความอยากรู้อยากเห็นเป็นดาวเรียกว่าไทเทเนียม Cas A ที่จะเป็นมหานวดาราประมาณ 9000 ปีแสงอยู่กับนิวตรอนเป็นดาวที่เป็นศูนย์ การระเบิดควรได้ observable บนโลกในนี้ศตวรรษที่ 17 กลาง แต่ไม่บันทึกดูเช่นกัน นี้มหานวดาราจะไม่ซ้ำกันที่จะผลิตเป็นประวัติการณ์มากเกิน 44Tiสัมพันธ์กับ 56Ni (ซึ่งผลิตในทั้งหมด supernovae) เนื่อง จากอุณหภูมิขั้น 5 ล้านเคลวินต้องสังเคราะห์ไทเทเนียม หดตัวความโน้มถ่วงอุณหภูมิเพิ่มขึ้นโดยตรงกับการมวลของดาว ดาวเดิมต้องมีขนาดใหญ่เป็นพิเศษวัตถุก่อนของลูกไอโซโทปที่อุดมสมบูรณ์ที่สุดของไทเทเนียมในโลกเช่นตี้-48 ซึ่งเป็นมีเสถียรภาพซึ่งไม่ได้เป็นผลิตภัณฑ์ ของการสังเคราะห์นิวเคลียสของดาวฤกษ์ แต่การสลายให้อนุภาคบีตาสแกนเดียมภาคพื้น 48 หรือวาเนเดียม 48ชอบอิตเทรียมและองค์ประกอบอื่น ๆ ส่วนใหญ่ที่หนักกว่าเหล็ก เซอร์โคเนียมและแฮฟเนียม syntheses เกิดในดาวผ่านการจับนิวตรอนบนไฟแช็กองค์ประกอบ แสดงความอุดมสมบูรณ์ของเซอร์โคเนียมในบรรยากาศของดาวฤกษ์บางsurprises, however. Like yttrium, it appears to be deficient in stars withlow metal content, but the ratios of these two elements relative to ironfluctuate from star to star, even when the stars are of similar types. However, there is less variability in abundances of these elements relative totitanium, which is puzzling.Another area of interest is the so-called zirconium conflict, whichrefers to a confusing situation observed in some HgMn stars where thespectral line corresponding to doubly ionized zirconium (Zr2+) is muchstronger than that belonging to the singly ionized atoms (Zr+). This iscounterintuitive, because more energy is required to remove two electrons than just one. A broadening of excitation energy levels within theatom might, however, cause an atomic emission line to appear dimmer. One way this could happen is through bombardment of zirconiumatoms by free-flying electrons, of which huge numbers exist in the hotgas of a star. This electron-impact broadening would have a greaterหน้า 16influence on Zr+ than on Zr2+, but the calculated effect is not enough toexplain the observed differences.The abovementioned anomalies indicate an incomplete scientificunderstanding of the dynamic processes within stellar atmospheres andinteriors and the need for more observational data.discovery and naming of TiTanium,Zirconium, and hafniumTitanium was discovered by the English clergyman, the Reverend William Gregor (1761–1817). A graduate of Cambridge University, Gregorserved several churches but spent most of his career as the rector ata church in Creed, England, from 1793 until 1817. Gregor’s friend,chemist John Warltire (1739–1810), introduced him to chemistry andmineralogy. Gregor was particularly attracted to mineralogy and waswell known for his analyses of England’s minerals. Intrigued by a blackmagnetic sand from his parish, he analyzed it and found it to be 46.56percent magnetite (an iron oxide), 3.5 percent silica, 45 percent anunknown reddish-brown substance, and 4.94 percent other material.Gregor showed his results to another friend, John Hawkins. Thetwo men agreed that the reddish-brown substance was a mineral thatmost likely contained a new element. Hawkins suggested naming thenew element menachanite after the Menachan Valley in which the sandhad been found. Gregor’s parish responsibilities prevented him frompursuing the matter further. Unfortunately, he died of tuberculosis in1817 without ever returning to his research.Because of Gregor’s declining health, menachanite was all but forgotten. In 1795, however, the German chemist Martin Heinrich Klaproth (1743–1817) began investigating a specimen of the mineral rutile(titanium oxide) from Hungary. From the rutile, he separated a metallicoxide whose properties remarkably resembled the properties of menachanite. Klaproth began studying both minerals, carefully comparingtheir properties, and concluded that they were the same metallic oxide.Although he gave William Gregor full credit for priority of discovery,Klaproth chose not to adopt Gregor’s name of menachanite for the newelement. Instead, deciding there were no special properties of the element or peculiarities regarding its origin, he chose a name that hadหน้า 17nothing to do with the element’s properties. Klaproth chose the nametitanium after the Greek gods called the Titans, the children of Uranusand Gaia.A number of minerals contain zirconium. Zircon, a trace mineralcommon to most granites, has been used as a gemstone since ancienttimes. Until nearly 1800, however, all analyses of zirconium mineralswere erroneous. They were reported to contain silica, iron oxide, alumina, lime (calcium oxide), and other minerals, but nothing that wouldhave been a new element.In 1789, Klaproth analyzed zircon and discovered that it containedthe mineral zirconia (later shown to be zirconium oxide, ZrO2). In 1824,Berzelius heated a sample of zirconia with potassium metal. Potassiumreduced the zirconium to an impure powdered form of the metal. During the next 90 years, chemists improved the process for isolating zirconium and gradually succeeded in obtaining samples of zirconium ofsuccessively higher purity. In 1914, a completely pure sample of zirconium was finally obtained by reducing zirconium tetrachloride (ZrCl4)with sodium. In the end, Klaproth was credited with zirconium’s discovery. The name zirconium itself was derived from the mineral zirconia.In 1911, an element was discovered that was believed to be a lanthanide, which would have placed its atomic number between 57 and 71.
After World War I, this element was found to occur mostly in titanium
ores and to be more similar to zirconium than to the lanthanides. The
Danish physicist Niels Bohr (1885–1962) suggested that this unknown
element was more likely a transition metal in the titanium family. In
1923, acting upon Bohr’s suggestion, the Hungarian chemist George
Charles de Hevesy (1889–1966) and his coworker, the German physicist
Dirk Coster (1889–1950), used X-ray analysis to prove that the atomic
number of the unknown element had to be 72, which placed the element after the lanthanide series and below zirconium. Although neither
de Hevesy nor Coster was Danish, the two men decided to name element 72 hafnium, after Bohr’s home of Copenhagen, Denmark.
The chemisTry of The TiTanium grouP
Titanium is element 22, with a density of 4.5g/cm3. Titanium is a silverywhite metal that is lighter and stronger than steel and very corrosion
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