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泵業(yè)金屬物理 化學特性
10貴金屬元素的基本物理性質是什么?
費金屬元素的基本物理化學性貢見表1.2。
11金、銀有哪些物理性質?
金、銀常見的形態(tài)分別為黃色和白色金屬。不同純度或不同顆粒度的金或銀的單質的顏色不同，如流傳已久的用試金石鑒定金的純度的方法——條痕比色， 有“七青、八黃、九紫、十赤”的結論，意思是條痕呈青、黃、紫和赤色的金的含量分別為70%、80%、90%和純金。隨著金銀顆粒度的減小，金或銀可以呈現(xiàn)色彩豐富的各種顏色，而顆粒度小到納米尺度時，無論是銀或金所呈現(xiàn)的顏色均為黑色。
金、銀均為面心立方晶體結構，晶胞參數(shù)a分別為0. 4079nm 和0.4086nm,晶格和晶胞參數(shù)上的相似性決定了金和銀特別容易形成互熔合金(固溶體)，而且金銀合金中金和銀的比例沒有任何限制。
金、銀都具有極為良好的可鍛性和延展性。金可壓成
0. 001mm厚的箔，這樣的金箔透明，所透過的光為綠色。金、銀可拉成直徑為0.001mm的細絲。
金和銀的導熱、導電性能非常好。銀的導電性勝過所有其他金屬，金僅次于銀和銅。金的蒸氣壓大大低于銀。銀的揮發(fā)性在高溫下相當高，且在氧化氣氛下比還原氣氛下更高。這特性在火法冶金中必須重視。
12金有哪些化學性質?
金的化學性質很穩(wěn)定，是唯一在高溫 下不與氧起反應的金屬。1000C下將金置于氧氣氣氛中40h，沒有檢測到失重，在1075C、1125C和1250C下于空氣中分別熔化金，經(jīng)1h后損失金的質量分數(shù)分別為0.009%、0. 10%和0.26%，這部分為“揮發(fā)”損失，而非氧化損失。
金具有寶貴的化學穩(wěn)定性的原因可以從電離能進行探討。決定金氧化態(tài)穩(wěn)定性的因素很多，通常要考慮完整的能量循環(huán)，需要用到元素的電離能、電子親和能和水合能等熱力學數(shù)據(jù)。由于許多離子及化合物缺乏這方面的數(shù)據(jù)，有時只能用電離能作為般指 導性判據(jù)。TB族元素的電離能如表1.3所示。
從第一電離能數(shù)據(jù)可見，金具有寶貴的化學穩(wěn)定性的原因在于Au具有很高的第一電離能。Au 的外層電子分布為4M54060，由于If和sd電子對核電荷的屏敞作用較弱，致使Au的6s電子受到較高的有效核電荷作用，不容易失去。
比較第二和第三電離能可以看出，Ag的第二電離能相對較
高，決定了它的主要氧化態(tài)是+1，而Au的第三電離能相對較低，導致Au易形成+3氧化態(tài)。由于Au的后幾級電離能也相對較小，因此Au存在Au (V)氧化態(tài)。
Cu、Ag和Au的電子親和能的理論值分別為118.3kJ/mol、125. 7]kJ/mol和222.2 73kJ/mol。可以看出，Au的電子親和能最高。
金的相對較高的電子親和能可與碘的電子親和能(295.3kJ/mol)相比較，因此有人把Au看作擬鹵素。已有的證據(jù)是化合物CsAu,可認為是CsAu-。基于Au有高的電離能和電子親和能，可以預料Au具有高的電負性值。根據(jù)Pauling 的電負性標度，Au的電負性為2.4,是所有金屬元素中最大的，比非金屬元素P的電負性(為2.1)大，而與非金屬元素C、S和I的電負性值(均為2.5)相近。渣漿泵廠家
據(jù)上所述，Au的化合物的性質與Cu、Ag化合物的性質的不同之處遠大于其相似之處。在許多情況下，把Au與周期表中同周期相鄰元素鉑和汞進行比較，比與同族的Cu、Ag比較更有價值。例如，存在著[AuCl2] 與HgCl2，[Au(PPhg)3J+與Au(PPh3)3以及[AuCl4]- 與[PtCl4]3- 的等電子配合物。
Physical and chemical characteristics of pump metal
What are the basic physical properties of precious metal elements?
See Table 1.2 for the basic physicochemical properties of the Fermi elements.
What are the physical properties of gold and silver?
The common forms of gold and silver are yellow and white metals respectively. The color of single gold or silver with different purity or particle size is different. For example, there is a long-standing method to identify the purity of gold with touchstone, i.e. streak color comparison. There is a conclusion that "seven cyan, eight yellow, nine purple and ten red" which means that the content of gold with stripes in cyan, yellow, purple and red is 70%, 80%, 90% and pure gold respectively. With the decrease of the particle size of gold and silver, gold or silver can present various colors with rich colors. When the particle size is small to nano scale, the color of silver or gold is black.
Gold and silver are both face centered cubic crystal structures, with cell parameters a of 0.4079nm and 0.4086nm, respectively. The similarity of lattice and cell parameters determines that gold and silver are particularly easy to form mutual melting alloy (solid solution), and there is no limit to the proportion of gold and silver in gold and silver alloy.
Gold and silver have excellent malleability and ductility. Gold can be pressed into
0. 001mm thick foil, so the gold foil is transparent and the light is green. Gold and silver can be drawn into 0.001mm diameter filaments.
Gold and silver have excellent thermal and electrical conductivity. Silver is more conductive than all other metals, and gold is second only to silver and copper. The vapor pressure of gold is much lower than that of silver. The volatility of silver is quite high at high temperature, and higher in oxidation atmosphere than in reduction atmosphere. This characteristic must be taken seriously in pyrometallurgy.
What are the chemical properties of gold?
Gold is the only metal that does not react with oxygen at high temperature. Gold was melted in air at 1075c, 1125c and 1250C for 40 hours at 1000C without any weight loss. After 1 hour, the mass fraction of gold lost was 0.009%, 0.10% and 0.26% respectively, which was "volatilization" loss rather than oxidation loss.
The reason why gold has precious chemical stability can be discussed from ionization energy. There are many factors that determine the stability of gold oxidation state. Generally, a complete energy cycle should be considered, and thermodynamic data such as ionization energy, electron affinity energy and hydration energy of elements should be used. Due to the lack of data in this field for many ions and compounds, sometimes only ionization energy can be used as a general guidance criterion. The ionization energy of TB group elements is shown in table 1.3.
It can be seen from the first ionization energy data that the reason for the valuable chemical stability of gold lies in the high first ionization energy of Au. The distribution of electrons in the outer layer of Au is 4m54060. Due to the weak shielding effect of if and SD electrons on the nuclear charge, the 6S electrons of Au are affected by higher effective nuclear charge, which is not easy to lose.
Comparing the second and third ionization energies, we can see that the second ionization energy of Ag is relatively higher
The main oxidation state of Au is + 1, but the third ionization energy of Au is relatively low, which leads to the formation of + 3 oxidation state. Since the latter ionization energy of Au is also relatively small, there is an oxidation state of Au (V).
The theoretical values of electron affinity of Cu, Ag and Au are 118.3kj/mol, 125.7] kJ / mol and 222.273kj/mol, respectively. It can be seen that AU has the highest electron affinity.
The relatively high electron affinity of gold can be compared with that of iodine (295.3kj / mol), so some people regard Au as a halogen like substance. The existing evidence is the compound csau, which can be considered as csau -. Based on the fact that AU has high ionization energy and electron affinity, it can be expected that AU has high electronegativity. According to Pauling's electronegativity scale, the electronegativity of Au is 2.4, which is the largest among all the metal elements, larger than that of P (2.1), and close to that of C, s and I (2.5). Slurry pump manufacturer
According to the above, the properties of Au compounds are much different from those of Cu and Ag compounds. In many cases, comparing Au with the neighboring elements of the same period in the periodic table, platinum and mercury, is more valuable than comparing Au with Cu and Ag of the same group. For example, there are isoelectronic complexes of [aucl2] with HgCl2, [Au (PPHG) 3j + with Au (PPh3) 3 and [AuCl4] - with [PtCl4] 3 -.
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