第十二章 氧族元素 Chapter 12

Oxygen Family Elements

Oxygen Sulphur Selenium O S Se Tellurium Polonium Te Po 也称为成矿元素 (ore-forming element)

§12-1 Oxygen and its compounds 一、 Simple substance 1. 除了 He 、 Ne 、 Ar 以外，氧与所有元素化合，只有与氟化合时，才呈还原性。 2. 最常见的氧化数为 -2, 还有 +2 (OF2) , +4[O(O2)] , +1(O2F2) , -1(H2O2) 3. 氧的单键离解能为 142KJ·mol-1 ，而硫为 268KJ·mol-1 。氧分子离解能为 494 kJ/m

ol

解释 : (1) 氧的原子半径小，孤对电子对之间有较大的排斥作用 (2) 氧原子没有空的 d 轨道，不能形成 d—p 键，

所以 O—O 单键较弱 对于 O2 分子而言，除了 σ 键外，还有二个三电子 π 键，所以 O2—2O 比较困难，要求加热到2000oC ，要求紫外光照射 氧元素在地球上的丰度最高，达 58%( 以 mol 计 )

二、 Compounds: 1. [-2]O.S. 最重要的化合物是水。 水分子轨道能级图如右图， 它解释了水存在四个第一电离 势。 分子轨道表示为：(σ S)

2(σ Z) 2(σ X

non) 2(πY

non)2

The 1s, 2s and 2pz orbitals of oxygen are symmetric (i.e., unchanged) with respect t

o all three symmetry operations. They are given the symmetry classification a1. The

2px orbital, since it possesses a node in the 2 plane (and hence is of different sign

on each side of the plane) changes sign when reflected through the 2 plane or whe

n rotated by 180° about the C2 axis. It is classified as a b2 orbital. The 2py orbital is a

ntisymmetric with respect to the rotation operator and to a reflection through the 1

plane. It is labelled b1.

   The hydrogen 1s orbitals when considered separately are neither unchanged nor changed in sign by the rotation operator or by a reflection through the 2 plane. Inst

ead both these operations interchange these orbitals. The hydrogen orbitals are said to be symmetrically equivalent and when considered individually they do not reflect the symmetry properties of the molecule. However, the two linear combinations  (1s1 + 1s2)  and  (1s1 - 1s2) do behave in the required manner. The

former is symmetric under all three operations and is of a1 symmetry while the latter is antisymmetric wit

h respect to the rotation operator and to a reflection through the plane 2 and is of b

2 symmetry.

   The molecular orbitals in the water molecule are classified as a1, b1 or b2 orbitals,

as determined by their symmetry properties. This labelling of the orbitals is analogous to the use of the and g-u classification in linear molecules. In addition to the symmetry properties of the atomic orbitals we must consider their relative energies to determine which orbitals will overlap significantly and form delocalized molecular orbitals.

The molecular orbitals in the water molecule are classified as a1, b1 or b2 orbitals, as dete

rmined by their symmetry properties. This labelling of the orbitals is analogous to the use of the and g-u classification in linear molecules. In addition to the symmetry properties of the atomic orbitals we must consider their relative energies to determine which orbitals will overlap significantly and form delocalized molecular orbitals.    The 1s atomic orbital on oxygen possesses a much lower energy than any of the other orbitals of a1 symmetry and should not interact significantly with them. The molecular orb

ital of lowest energy in H2O should therefore correspond to an inner shell 1s atomic-like

orbital centred on the oxygen. This is the first orbital of a1 symmetry and it is labelled la1.

Reference to the forms of the charge density contours for the la, molecular orbital substantiates the above remarks regarding the properties of this orbital. Notice that the orbital energy of the la1 molecular orbital is very similar to that for the 1s a

tomic orbital on oxygen. The 1a1 orbital in H2O is, therefore, similar to the l inner shell m

olecular orbitals of the diatomic hydrides.    The atomic orbital of next lowest energy in this system is the 2s orbital of a1 symmetry

on oxygen. We might anticipate that the extent to which this orbital will overlap with the (1s1 + 1s2) combination of orbitals on the hydrogen atoms to form the 2a1 molecular orbita

l will be intermediate between that found for the 2 molecular orbitals in the diatomic hydrides CH and HF. The 2 orbital in CH results from a strong mixing of the 2s orbital on carbon and the hydrogen 1s orbital. In HF the participation of the hydrogen orbital in the 2 orbital is greatly reduced, a result of the lower energy of the 2s atomic orbital on fluorine as compared to that of the 2s orbital on carbon.

   Aside from the presence of the second proton, the general form and nodal structure of the 2a1 density distribution in the water molecule is remarkably similar to the 2

distributions in CH and HF, and particularly to the latter. The charge density accumulated on the bonded side of the oxygen nucleus in the 2a1 orbital is localized nea

r this nucleus as the corresponding charge increase in the 2 orbital of HF is localized near the fluorine. The charge density of the 2a1 molecular orbital accumulated in

the region between the three nuclei will exert a force drawing all three nuclei together. The 2a1 orbital is a binding orbital.

   Although the three 2p atomic orbitals are degenerate in the oxygen atom the presence of the two protons results in each 2p orbital experiencing a different potential field in the water molecule. The nonequivalence of the 2p orbitals in the water molecule is evidenced by all three possessing different symmetry properties. The three 2p orbitals will interact to different extents with the protons and their energies will differ.    The 2px  orbital interacts most strongly with the protons and forms an orbital of b2 s

ymmetry by overlapping with the (1s1 - 1s2) combination of 1s orbitals on the hydrog

ens. The charge density contours for the lb2 orbital indicate that this simple LCAO d

escription accounts for the principal  features of this molecular orbital. The lb2 orbital

concentrates charge density along each O-H bond axis and draws the nuclei together. The charge density of the 1b2 orbital binds all three nuclei. In terms of the forces

exerted on the nuclei the 2a1 and lb2 molecular orbitals are about equally effective in

binding the protons in the water molecule.

The 2pz orbital may also overlap with the hydrogen 1s orbitals, the (1s1 + 1s2) a1

combination, and the result is the 3a1 molecular orbital. This orbital is concentra

ted along the z-axis and charge density is accumulated in both the bonded and nonbonded sides of the oxygen nucleus. It exerts a binding force on the protons and an antibinding force on the oxygen nucleus, a behaviour similar to that noted before for the 3 orbitals in CH and HF.     The 2py orbital is not of the correct symmetry to overlap with the hydrogen 1s

orbitals. To a first approximation the 1b1 molecular orbital will be simply a 2py at

omic orbital on the oxygen, perpendicular to the plane of the molecule. Therefore, the 1b1 orbital does resemble a 2p atomic orbital on oxygen but one which is

polarized into the molecule by the field of the protons. The 1b1 molecular orbital

of H2O thus resembles a single component of the 1molecular orbitals of the d

iatomic hydrides. The 1b1 and the 1 orbitals are essentially nonbinding. They e

xert a small binding force on the heavy nuclei because of the slight polarization. The force exerted on the protons by the pair of electrons in the 1b1 orbital is slig

htly less than that required to balance the force of repulsion exerted by two of the nuclear charges on the oxygen nucleus. The 1b1 and 1 electrons basically

do no more than partially screen nuclear charge on the heavy nuclei from the protons.   

In summary, the electronic configuration of the water molecule as determined by molecular orbital theory is

1a212a2

11b223a2

11b21

The la1 orbital is a nonbinding inner shell orbital. The pair of electr

ons in the la1 orbital simply screen two of the nuclear charges on t

he oxygen from the protons. The 2a1, 1b2 and 3a1 orbitals accumul

ate charge density in the region between the nuclei and the charge densities in these orbitals are responsible for binding the protons in the water molecule. Aside from being polarized by the presence of the protons, the lb1 orbital is a non-interacting 2py orbital on the

oxygen and is essentially nonbinding.

http://www.chemistry.mcmaster.ca/esam/Chapter_8/section_6.html

Contents from http://butane.chem.uiuc.edu/pshapley/312/Lectures/L10/index.html

B2

A1

2px B1

2py B2

2px B1

2py B2

2px B1

2py B2

http://www.chemistry.mcmaster.ca/esam/Chapter_8/section_6.html#Fig_8-11.

Contour maps of the molecular orbital charge densities for H2O. The maps for the la1, 2a1,

3a1and 1b2 orbitals (all doubly-occupied) are shown in the plane of the nuclei. The lb1 or

bital has a node in this plane and hence the contour map for the 1b1 orbital is shown in th

e plane perpendicular to the molecular plane. The total molecular charge density for H2O

is also illustrated. The density distributions were calculated from the wave function determined by R. M. Pitzer, S. Aung and S. I. Chan, J. Chem. Phys. 49, 2071 (1968).

2. [ -1 ] O.S. The most important peroxide is that of

hydrogen

(1) Structure:

是极性分子，即两个氢原不在同一个平面 (2) Properties:

它是一个极好的离子性溶剂，与水互溶，这是由于能形成新的 hydrogen bond , 在实验室中常用3%—30% 的过氧化氢水溶液称为双氧水（ perhydro

l ）

b. H2O2 是一种弱酸 H2O2 + H2O = H3O+ + HO2

-

c. 在酸性条件下， H2O2 是极好的氧化剂， 在碱性条件下， H2O2 是中等的氧化剂。 过氧化氢在水溶液中，不论是氧化剂，还是还原剂，都在反应体系中不引入任何杂质： 2H+ + H2O2 + 2e 2H2O O2 + 2H+ + 2e H2O2

d. 从上面的电位图来看 H2O2 不稳定 (i) 在 OH- 介质中比 H+ 介质中分解快 (ii) 若有重金属离子 Fe2+ , Mn2+ , Cu2+ , Cr2+ 等都大大加快 H2O2 的分解 (iii) 波长为 320—380nm 的光促使 H2O2

分解 (iv) 受热加快分解

A ： OHOHO 2V77.1

22V68.0

2

在碱性条件下，H2O2 是中等的氧化剂。

B ： OHHOO 2V878.0

2V076.0

2

http://pubs.acs.org/doi/full/10.1021/ja411705d

Bubble-Propelled Micromotors

(3) Preparation: a. BaO2 + H2SO4 = BaSO4↓ + H2O2

BaO2 + CO2 + H2O = BaCO3 + H2O2 b. 电解—水解法 电解： 2NH4HSO4 = (NH4)2S2O8 + H2↑ 过二硫酸铵发生水解 : (NH4)2S2O8 + 2H2SO4 = H2S2O8 + 2NH4HSO4 H2S2O8 + H2O = H2SO4 + H2SO5

H2SO5 + H2O = H2SO4 + H2O2

O

O....

HO

SOHO

O O

S S

HO OH

OOO O........ ...

.

. ...

C. 乙基蒽醌法 : H2 + O2 = H2O2 ( 乙基蒽醌为催化剂 ) (4) Application: 利用 H2O2 的氧化性，可漂白毛、丝织物 火箭的氧化剂 用来恢复古画的色彩 利用 H2O2 的还原性，可以除 Cl2

3% 的 H2O2 可做杀菌剂

+ H2

H2 + O2

乙基蒽醌

钯H2O2

22OPd OH 2 　 　 　

O

O

C2H5

O

O

C2H5

C2H5

OH

OH

2-乙基蒽醇

27222 OCrOH42H O5H 2 2

(5) Identification: 在重铬酸盐的酸性溶液中，加入少许乙醚和过氧化氢

溶液并摇荡，乙醚层出现蓝色的 [CrO(O2)2·(C2H5)2O]

此法可用来鉴别铬，同时可确认是 CrO42-或 Cr2O7

2-

若不加乙醚，水溶液中的 CrO5再与 H2O2 反应，放出O2↑

Cr

O

O

O

O

O

2CrO(O2)2 + 7H2O2 + 6H+ 2Cr3+ + O2↑+ 10H2O

3. [ I , II , IV ] O.S. O2F2 , OF2 , O(O2) (1) O2F2 dioxydifluoride : 反磁性分子，与 H2O2结构类似，红色挥发性液体 O2 + F2 = O2F2 不稳定 O2F2 + PtF5 = O2

+[PtF6-] + 1/2F2

此反应中 O2F2 即是氧化剂又是还原剂

(2) OF2 Oxygen difluoride: 非直线型分子，有毒，浅黄色气体，是强氧化剂和氟化剂 2F2 + 2NaOH = OF2 + 2NaF + H2O (3) O3 Ozone: 可看作 O(O2) ，实际上是 O2 的同素异形体（ allotrope ）

a. 它是反磁性物质（ diamagnetic material ） 它有两个 σ 键，一个 3

4Π 。即中心氧原子采取 SP2 杂化，其中两个单电子轨道与另外二个原子形成两个 σ 键，第三个杂化轨道有一对孤电子

对，形成 σnon 。 b. Physical properties

它是一种非常毒的蓝色气体，有特殊的腥臭味；少量 O3 可以净化空气、大量 O3 对人体有害。

液态 O3 是深蓝色，固态 O3 是暗紫色，由于O3 的极化作用与极化率都大于 O2 ，所以其熔沸点比 O2 高，比 O2易溶于水，有颜色。 c. Chemical properties:

∆G= -326KJ·mol-1

其氧化能力大于 O2 ，如： O3 + XeO3 + 2H2O = H4XeO6 +O2↑

PbS + 4O3 = PbSO4 + 4O2↑

2I- + O3 + H2O = I2 + O2 + 2OH- 可以定量测定 I-

O32O 23

d. Preparation: 3O2 = 2O3 条件为放电或 hv ，所以在高空约 25 km 处有一臭氧层 e. Applications: 臭氧可氧化 CN- 而解毒，故常用来治理电镀工业中的含氰废水，不会引起二次污染 氧化有机物，可把烯烃氧化并确定双键的位置 :CH3CH2CH=CH2 CH3 CH2CHO + HCHOCH3CH=CHCH3 2CH3CHO

O3

O3

§12-2 Sulfur and its compounds一、 The simple substance 1. 在自然界中存在天然单质的硫，主要在火山区，这是因为 2H2S + SO2 = 3S↓ + 2H2O 2H2S + O2 = 2S↓ + 2H2O 反应物中的 H2S 来自地下硫化物矿床与高温水蒸汽的反应

2. Allotrope : (1) S8 ：最稳定的形式，成环状（ ring ）或皇冠状（ crown ） 它有两种形式： 斜方（正交）硫（ orthorhombic ）呈黄色； 单斜硫（ monoclinic ）呈浅黄色。 (2) Allotrope 的转化 S2 是顺磁性的，而 S4 , S6 , S8 …… 都是反磁性

的

3. Chemical properties (1) 与非金属（除稀有气体、 N2 、 I2 ）、金属

（除 Au 、 Pt ）的反应2Al + 3S = Al2S3 Fe + S = FeSHg + S = HgS ( 研磨 ) S + O2 = SO2 (2) 在沸腾的碱液中发生歧化3S + 6NaOH = 2Na2S + Na2SO3 + 3H2O 4. preparation3FeS2 + 12C + 8O2 = Fe3O4 + 12CO + 6S

二、 Compounds 1. [ -2 ]O.S. (1) Hydrolysis S2- + H2O = HS- + OH-

SiS2 + 3H2O = H2SiO3 + 2H2S Al2S3 + 6H2O = 2Al(OH)3 + 3H2S (2) interaction: Na2S + CS2 = Na2CS3

Na2CS3 + H2SO4 = Na2SO4 + H2CS3

H2CS3 = H2S + CS2

(3) reduction: 其氧化产物为 S 、 SO2 、 H2SO4 ，取决于反应条件 2KMnO4 + 5H2S + 3H2SO4 = 2MnSO4 + 5S↓ + K2SO4 + 8H2O 2H2S + O2 = 2S↓ + 2H2O H2S + I2 = 2HI + S↓ H2S + 4Br2 = 4H2O + H2SO4 + 8HBr

(4) 许多硫化物有颜色且难溶于水，可用于分离，鉴别阳离子

随着原子序数增加，颜色加深，这主要是硫化物中共享的离域键增加

(5) 硫化物可分成导体、半导体和绝缘体e.g. TiS2: Metallic conductivity ，ZrS2: Semiconductivity ，HfS2: Dielectric

As2S3yellow ZnS White Ga2S3

Yellow GeS2White

Sb2S3orange CdS Yellow In2S3

Yellow SnS2Yellow

Bi2S3black HgS black Tl2S3

black PbS black

2. [ -2/n ] O.S. 多硫化物 ( polysulfide or persulfide ) (1) Na2S + (n-1)S = Na2Sn 酸化

H2Sn (NH4)2S + (N-1)S = (NH4)2Sn 氢离子

(2) Redox reactions: 3Na2S2 + As2S3 = 2Na3AsS4 + S 4FeS2 + 11O2 = 2Fe2O3 + 8SO2

H2S + (n-1)S

3. [ +4 ] O.S. SHal4 （ SF4 ） SOHal2 （ SOF2 、 SOCl2 ） SO2

(1) 与 H2O 反应 SO2 + H2O = H2SO3

不能从水溶液中分离出来，是相当强还原剂 SOCl2 + 2H2O = 2HCl + H2SO3 SF4 + 3H2O = 4HF + H2SO3

(2) 既是氧化剂，又是还原剂，能发生歧化反应 SO2 +H2S = 3S + 2H2O SO2 + Br2 + 2H2O = H2SO4 + 2HBr 4Na2SO3 = 3Na2SO4 + Na2S （加热）

4. [ +6 ] O.S.(1) 浓硫酸的特性：吸水性，脱水性，氧化性，钝化性等。(2) SF6: SF6 + 3H2O = SO3 + 6HF 虽然在水溶液中∆ G<<0 ，但 SF6非常稳定，不与水反应，这显然是动力学因素控制该反应。 SF6 不与碱酸反应，这是由于中心原子的价 (+6) 与配位数 (6) 饱和所产生的动力学因素，以及高的电离能所致（ 19.3 ev ） , SF6 是电介质，且分子量大，所以作为高压发电机中的气相绝缘体。

(3) S(VI) 的含氧化合物中的配位数为 4 ，所以 SO3很容易聚合（ polymerize ），如右图。 SO3 + HF =H[SO3F] 其中 HSO3F 的酸性与 HClO4

一样强，而 SbF5· HSO3F 称为超酸。

“Superacid” and “Superbase”

Olah received the 1994 Nobel Prize in Chemistry for his pioneering research on carbocations and their role in the chemistry of hydrocarbons. In particular, he developed superacids (a term he coined) that are much stronger than ordinary acids, are non-nucleophilic, and are fluid at low temperatures. In such media (examples include HF-SbF5 and SbF5-SO2ClF-SO2F2) carbocations are sta

ble and their physical properties, such as NMR spectra, can be observed, thus allowing details of their structures to be determined. Besides trivalent ions, of which CH3

+ is the parent, Olah demonstrated the existence of higher coordinate carbocations such as CH5

+. These specie

s do not violate the octet rule, but involve 2-electron 3-center bonding.Olah was born and educated in Hungary, moved to Canada (Dow Chemical) after the 1956 Hungarian uprising, and ultimately to the U.S.A. He was professor and chairman of chemistry at Case Western Reserve University before moving to the University of Southern California, where he is distinguished professor at USC's Loker Hydrocarbon Research Institute. Olah's many honors besides the Nobel include the ACS awards in Petroleum Chemistry(1964) and for Creative Work in Synthetic Organic Chemistry (1979), and the Roger Adams Award in Organic Chemistry (1989).

George Andrew OlahHungarian–American chemist (192

7–) Olah's "magic acid", so-named for its ability to attack hydrocarbons, is prepared by mixing antimony pentafluoride (SbF5) and fluorosulfuric acid. The nam

e was coined after one of Professor Olah's post-doctoral associates placed a candle in a sample of magic acid. The

candle was dissolved, showing the ability of the acid to protonate hydrocarbo

ns (which are not basic).

“Superacid” and “Superbase”

A superacid is an acid with an acidity greater than that of 100% sulfuric acid, which has a Hammett acidity function of -12. Commercially available superacids include trifluoromethanesulfonic acid (CF3SO3H), also known as triflic acid, and fluorosulfuric acid (FSO3H), both of which are about a thousand times stronger (i.e. have more negative H0 values) than sulfuric acid. The strongest superacids are prepared by the combination of two components, a strong Lewis acid and a strong Brønsted acid. The strongest super acid system, the so-called fluoroantimonic acid, is a combination of hydrogen fluoride and SbF5. In this system, HF releases its proton (H+) concomitant with the binding of F− by the antimony pentafluoride. The resulting anion (SbF6

−) is both a weak nucleophile and a weak base. The proton effectively becomes "naked", which accounts for the system's extreme acidity. Fluoroantimonic acid is 2×1019 times stronger than 100% sulfuric acid, and can produce solutions with a pH down to –25.

“Superacid” and “Superbase”

In chemistry, a superbase is an extremely strong base. There is no commonly accepted definition for what qualifies as a superbase, but most chemists would accept sodium hydroxide as a 'benchmark' base just as sulfuric acid is a 'benchmark' acid (see superacid). The hydroxide ion is a good benchmark because it is the strongest base that can exist in a water solution; stronger bases neutralize water as an acid by deprotonation, to produce hydroxide (and protonated superbase). Another use that can define superbase is stoichiometric α-deprotonation of a carbonyl compound into an enolate, something that cannot be done by "regular bases". Despite this, the term still doesn't have a standard chemical definition, so for example Proton Sponge may be called "superbase". Organometallic compounds of reactive metals are usually superbases, for example organolithium and organomagnesiums (Grignard reagents). Another type of organic superbase has a reactive metal exchanged for a hydrogen on a heteroatom, such as oxygen (unstabilized alkoxides) or nitrogen (lithium diisopropylamide).

“Superacid” and “Superbase”

Reactions involving superbases are usually water-sensitive, conducted under an inert atmosphere and at a low temperature. A desirable property in many cases is low nucleophilic reactivity, i.e. a non-nucleophilic base. Unhindered alkyllithiums, for example, cannot be used with electrophiles such as carbonyl groups, because they attack the electrophiles as nucleophiles.In organic synthesis, the Schlosser base (or Lochmann-Schlosser base), i.e. the combination of n-butyllithium and potassium tert-butoxide, is a commonly used superbase. Butyllithium exists as four-, or six-membered clusters, which are kinetically slow to react. The tertiary alcoholate (butoxide) serves to complex the lithium ion, which breaks the butyllithium clusters. This makes the butyllithium kinetically more reactive.Inorganic superbases are typically salts with highly charged, small negative ions, e.g. lithium nitride, which has extreme negative charge density and so is highly attracted to acids, like the aqueous hydronium ion. Alkali and earth alkali metal hydrides (sodium hydride, calcium hydride) are superbases.

(4) 硫代硫酸盐（ thiosulphates ） a. 沸腾温度下，亚硫酸钠溶液与 S 粉混和 SO3

2- + S = S2O32- 或者

2Na2S + Na2CO3 + 4SO2 = 3Na2S2O3 + CO2 （价态变化）

b. 这两种硫是不等价的

c. 不稳定，在酸性条件下分解，只有 PH >4.6 时才不分解 d. 是一种还原剂，也是一种络合剂 2Na2S2O3 + I2 = Na2S4O6 + 2NaI AgBr + 2Na2S2O3 = Na3[Ag(S2O3)2] + NaBr

OHSOSSOSSOS 223235H2

332352

33235

沸腾

(5) 连硫酸及其盐 a. 通式： H2SxO6 ( X=2—6 ) b. 连硫酸不稳定，易分解 H2S2O6 = H2SO4 + SO2

H2S4O6 = H2SO4 + SO2 + 2S

c. 制备 2MnO2 + 3H2SO3 = MnSO4 + MnS2O6 + 3H2O BaS2O6 + H2SO4 = BaSO4↓ + H2S2O6

SHO S

SOH

O O

O O

trithionic acidH2S3O6

SHO

O

O

S

SS

OHO

Otetrathionic acid

H2S4O6

(6) 当 SO3 溶于浓 H2SO4 中时，产生 H2SO4·nSO3— 多硫酸，其中最重要的是 H2S2O7焦硫酸。 H2SO4 , H2S2O7 , H2S3O10 , H2S4O13

的混合物称为发烟硫酸。 H2SO4·nSO3 + nH2O = (n+1)H2SO4

5. 特殊氧化态 (1) [ +1 ]O.S. S2O 其结构为 SSO

3S + SO2 = 2S2O ( 放电，加热 )

(2) [ +3 ]O.S. 连二亚硫酸及其盐 （ dithionous acid ）

a. 二元弱酸 b. 制备 2NaHSO3 + Zn = Na2S2O4 + Zn(OH)2

2Na[Hg] + 2SO2 = Na2S2O4 + 2Hg c. 在 OH －介质中能把硝基化合物还原成胺 d. 能发生歧化反应

SS

O( 8e) ( 8e)SS

O SS

O( 10e)共振结构式为

OHOS2 2242 3

232 2HSOOS

N S

S

N S

N1.66 A

o

89.6°

90.4°

SNS

S

S

S

S

S

S

SN

N

N

N

N

N

N

硫的氮化物（ sulfur-nitrogen compounds ）

64

§12-3 The selenium subgroup (Selenium, Tellurium, Polonium) 一、 General properties: 1. Se 和 Te 是稀散元素（ scattered elements ） , Po 是稀有元素（ rare elements ） 2. Coordination number: S 、 Se 与 O 原子配位3 , 4 , Te 与 O 原子配位达 6 3. 最高氧化态稳定性 SF6>SeF6<TeF6 PoF6>SF6

二、 Simple substances 1. Se 不与水、稀酸反应 Te + 2H2O = TeO2 + 2H2↑ Po + 2HCl = PoCl2 + H2↑ 2. Se 与 Te 可被 HNO3 氧化 3Se + 4HNO3 （稀） + H2O = 3H2SeO3 + 4NO↑

3. Disproportination: 3E + 6KOH = K2EO3 + 4K2E + 3H2O

E=Se, Te

Po + 8HNO3 Po(NO3)4 + 4NO2 + 4H2O

3. Preparation: 制备 H2SO4 时，用 MnO2 氧化金属硒化物或碲化物得 S

eO2 ,TeO2 ,然后 EO2 + 2SO2 = E + 2SO3

三、 Compounds: 1. [-2 ] O.S. H2Se , H2Te (1) 酸性 : H2Te>H2Se>H2S (2) 还原性 : H2Te>H2Se>H2S (3) 制备—水解法： Al2Se3 + 6H2O = 3H2Se + 2Al(OH)3

Al2Te3 + 6H2O = 3H2Te + 2Al(OH)3

2. [ +2 ] O.S. TeCl2 , SeCl2 不稳定 2TeCl2 = TeCl4 + Te 2SeCl2 + 3H2O = H2SeO3 + Se + 4HCl

3. [ +4 ] O.S. （氧化性） SO2 SeO2 TeO2 酸性、还原性减弱，氧化性增强

遇强氧化剂时显还原性： 3TeO2 + H2Cr2O7 + 6HNO3 + 5H2O = 3H6TeO6 + 2Cr(NO3)3

H2SeO3 + H2O2 = H2SeO4 + H2O

4. [ +6 ] O.S. SeO3 , TeO3

(1) Preparation: K2Se + 4NaNO3 = K2SeO4 + 4NaNO2 （加热） K2SeO4 + SO3 = K2SO4 + SeO3

H6TeO6 = TeO3 + 3H2O （加热）

(2) H6TeO6 , SeO42- 的氧化性比 H2SO4强

H2SeO4 + 2HCl = H2SeO3 + Cl2 + H2O

H2SeO4—HCl 的混合液可溶解金和铂 Se , Te 的化合物均非常毒（ toxic ）