Who has information about multi center keys!! 50

Atoms such as boron and aluminum have less valence electrons than valence orbitals, and when they form compounds, they show a distinct tendency to be electron-deficient. For example, in compounds such as borane and alkyl aluminum, multicentric bonds occur because there are not enough valence electrons for the chemical bond between all two atoms to be a normal two-electron bond. In the case of ethylborane b2H6, the boron atom is close to the tetrahedral configuration, but it has only 12 valence electrons in total.

The boron-hydrogen bonds at the four ends share 8 valence electrons, and the remaining 4 valence electrons are distributed in two boron-hydrogen-boron bridge bonds to form two three-center-two-electron multi-center bonds. In the more complex boranes, there are also multi-center bonds formed by three-center-two-electron boron-boron-boron bridge bonds, etc.

multi-center key; multicenter bond

Molecular Formula: CAS Number:

Properties: A covalent bond formed by multiple atoms sharing a number of electrons. Boranes and clusters of metal atoms often have multiple central bonds.

Such as ethylborane B2H6, which has a bridge structure. In each bh2 group, the b atom still has one electron and two orbitals to further bond, and the boron atom in the 2 bh2 group is bonded with the two hydrogen atoms to form two b—h—b three-center two-electron bonds. Electron-deficient molecules, in particular, tend to form polycentric bonds.

A multi-center bond is actually a delocalized bond, which is relative to a localized bond that is positioned between two atoms.

First of all, this is an anion, not a bh compound in the general sense, if explained by the styx rule, there are 12 b atoms must lack 12 electrons, so there are 12 b-h-b or b-b-b (it is not easy to play on the computer, anyway, it is 3 center double electrons), obviously the anion does not contain b-h-b, so it is 12 b-b-b, and there are 12 normal b-h bonds.

To put it simply, all keys between b-b are multi-center keys, while b-h keys are not shared.

More than 500 at a time, you have to do one course of treatment, ten times of a course of treatment. At this moment, I'm doing it!!

More than 1,000 at a time, ear red light is more expensive, and an anti-inflammatory effect will be charged more than 400 at a time, it's really messy, these hospitals. Argon ions are a set of things, in fact, to give you a massage. It didn't work at all.

, boron and silicon are in a diagonal line in the periodic table, their ionic polarization forces are close to each other, and there are many similarities in properties 1 Boron is 4 or 3 in the molecule of a compound depending on the number of hybrid orbitals 5 polycentric bonds refer to.

Chemical bond refers to the strong interaction force between two or more adjacent atoms (or ions) within a molecule or crystal.

There are 3 limit types of chemical bonds, namely ionic bonds, covalent bonds, and metallic bonds. Ionic bonds are the mutual attraction of oppositely charged ions, such as chlorine and sodium bonded to NaCl. A covalent bond is an attraction created by two or more atoms by sharing a pair of electrons, and a typical covalent bond is formed by two atoms by attracting a pair of bonding electrons.

For example, two hydrogen nuclei attract a pair of electrons at the same time, forming a stable hydrogen molecule. Metallic bonds, on the other hand, are interactions that bind metal atoms together and can be seen as highly delocalized covalent bonds. A chemical bond that is positioned between two atoms is called a localized bond.

A polycentric bond formed by the common electrons of multiple atoms is called a delocalized bond. The metal ions are fixed to the lattice junction and are in the "ocean" of delocalized electrons. In addition to this, there are also transition types of chemical bonds:

Due to the difference in the magnitude of the attraction of particles to electrons, the covalent bond that skews the bond electrons to one side is called a polar bond, and the chemical bond that provides the bonding electrons by one side is called a coordination bond. The limits of both ends of a polar bond are ionic and non-polar bonds, and the limits of both ends of a delocalized bond are a localized bond and a metallic bond.

Polar bondsIn compound molecules, the covalent bonds formed by different kinds of atoms are inevitably biased due to the different abilities of the two atoms to attract electrons.

Relative electropositive to the side of the atom with the stronger ability to attract electrons, and therefore to the side of the atom with the weaker ability to attract electrons. Such covalent bonds are called polar covalent bonds, or polar bonds for short.

Non-polar bonds. Covalent bonds formed between atoms of the same element are called nonpolar covalent bonds. The ability of the same atom to attract the shared electron pairs is equal, the bonding electron pairs are evenly distributed between the two nuclei, not biased towards any one atom, and the bonding atoms are not electrically charged. Non-polar bonds can exist in elemental molecules (e.g., H—H bonds in H2, O O bonds in O2, N N bonds in N2) or in compound molecules (e.g., C—C bonds in C2H2).

The bond dipole moment of a non-polar bond is 0. The molecules formed by the combination of non-polar bonds are all non-polar molecules. The bonds present in a non-polar molecule are not all non-polar bonds, if a polyatomic molecule coincides with the geometric center of positive charge and the geometric center of negative charge on the spatial structure, then it is also a non-polar molecule even if it consists of polar bonds.

Crystals formed by the bonding of non-polar bonds can be atomic crystals, mixed crystals, or molecular crystals. For example, there are three types of allotropes in carbon element: regular tetrahedral skeleton diamond (atomic crystal), layered graphite (hybrid crystal) can be formed by relying on C-C non-polar bonds, and spherical carbon molecule fullerene C60 (molecular crystal) can also be formed

The Yellow River, a major river in northern China, has a total length of about 5,464 kilometers and a basin area of about 752443 square kilometers. It is one of the longest rivers in the world and the second longest river in China.

The northern source of the Yellow River originates from the Zhaqu at the southern foot of the Chahasila Mountain, a branch of the Bayankala Mountains on the Qinghai-Tibet Plateau in Qinghai Province, the southern source originates from the Kariqu at the northern foot of the Gezigoya Mountain, the branch of the Bayan Kala Mountains, and the western source originates from the Yougu Zongliequ in the western part of the Xingzhu Haixi. It flows from west to east through 9 provinces (autonomous regions) of Qinghai, Sichuan, Gansu, Ningxia, Inner Mongolia, Shaanxi, Shanxi, Henan and Shandong, and finally flows into the Bohai Sea.

The middle and upper reaches of the Yellow River are mainly mountainous, and the middle and lower reaches are dominated by plains and hills. Because the middle section of the river flows through the Loess Plateau region of China, it carries a large amount of sediment, so it is also known as the river with the most sediment content in the world. But in Chinese history, the diversion of the lower reaches of the Yellow River has had a huge impact on human civilization.

The Yellow River is our mother river, let's get to know our great mother!

The Yellow River is also known as the Yellow River in ancient China, also known as the Turbid River and the China River. It originates in the Bayankala Mountains of Qinghai Province, People's Republic of China, flows through 9 provinces and regions of Qinghai, Sichuan, Gansu, Ningxia, Inner Mongolia, Shaanxi, Shanxi, Henan and Shandong, and finally flows into the Bohai Sea in Kenli County, Dongying, Shandong Province. The total length of the main stream is 5,464 kilometers, second only to the Yangtze River and the second longest river in China.

The Yellow River is also the fifth longest river in the world.

The Yellow River is 3,472 kilometers long from its source to Hekou Town, Tuoketuo County, Inner Mongolia Autonomous Region. The middle reaches are from Hekou Town to Taohuayu in Zhengzhou, Henan Province, with a river length of 1,206 kilometers; The lower reaches of Taohuayu are 786 kilometers long. The Yellow River runs through the east and west of China, with a basin of 1,900 kilometers long from east to west and 1,100 kilometers wide from north to south, with a total area of 752443 square kilometers.

The Yellow River, like a lion with its back rising and its head high, crosses the lofty mountains and mountains of Qinghai and Gansu provinces from the Qinghai-Tibet Plateau; the Hetao Plain across Ningxia and Inner Mongolia; galloping in the high mountains and deep valleys between Jin and Shaanxi; Break through the "dragon gate", turn around at the foot of Xiyuehua Mountain, cross the North China Plain, and rush to the shore of the Bohai Sea. It flows through 9 provinces and regions, brings together more than 40 major tributaries and more than 1,000 streams, travels 5,464 kilometers, and covers a basin area of more than 750,000 square kilometers, making it the second largest river in China. The average annual precipitation of the whole basin is about 400 mm, and the average annual runoff of the Yellow River is only 57.4 billion cubic meters, ranking eighth among Chinese rivers.

In the basin, together with the downstream Henan and Shandong riverside areas, there are more than 200 million acres of cultivated land and about 100 million people.

The average annual natural runoff of the Yellow River is 58 billion cubic meters, the average annual runoff depth is 77 mm, the per capita water volume of the basin is 593 cubic meters, and the average water volume per mu of cultivated land is 324 cubic meters.

The middle reaches of the Yellow River flow through the Loess Plateau, and its tributaries bring in a lot of sediment, making it the most sediment-laden river in the world. The maximum annual sediment transport reached 100 million tons (1933), and the highest sediment content was 920 kilograms and cubic meters (1977). The average sediment transport capacity of Sanmenxia Station is about 1.6 billion tons for many years, and the average sediment content is 35 kilograms of cubic meters.

Length 5464 km.

The source is 4800 meters above sea level.

The average flow rate is cubic meters in seconds.

The basin covers an area of 752443 square kilometers.

Source: Qinghai Province.

Injected into the Bohai Sea.

Flowing through the country People's Republic of China.

The Yellow River, the second largest river in China. It originates from the ancient Zonglie Basin at the northern foot of Bayankala Mountain on the Qinghai Plateau, meanders eastward, crosses the Loess Plateau and the Huanghuaihai Plain, and flows into the Bohai Sea. The total length of the main stream is 5,464 kilometers, and the water surface difference is 4,480 meters.

The total area of the basin is 10,000 square kilometers (including the area of the inflow area is 10,000 square kilometers).

In ancient China, it was also known as a river, which originated in the Bayankala Mountains of Qinghai Province of the People's Republic of China, flowed through 9 provinces and regions of Qinghai, Sichuan, Gansu, Ningxia, Inner Mongolia, Shaanxi, Shanxi, Henan and Shandong, and finally emptied into the Bohai Sea in Kenli County, Dongying, Shandong Province.

The topographic area through which the main stream of the Yellow River flows is the Qinghai-Tibet Plateau-Loess Plateau-Inner Mongolia Plateau-North China Plain in order from upstream to downstream.

The Qinghai-Tibet Plateau crosses the lofty mountains of Qinghai and Gansu provinces; the Hetao Plain across Ningxia and Inner Mongolia; Galloping in the high mountains and deep valleys between Jin and Shaanxi, turning east at the foot of Xiyue Huashan, crossing the North China Plain, rushing to the shore of the Bohai Sea. It flows through 9 provinces and districts, bringing together more than 40 major tributaries and more than 1,000 streams.

The main tributaries of the Yellow River include the Bai River, the Hei River, the Huangshui River, the Zuli River, the Qingshui River, the Dahei River, the Kuye River, the Wuding River, the Fen River, the Wei River, the Luo River, the Qin River, the Dawen River, etc.

The main lakes on the Yellow River are Zhaling Lake, Ngoling Lake, Wuliangsuhai Lake, and Dongping Lake.

Mainstream Canyon. There are 30 canyons on the main stream of the Yellow River, 28 in the upper reaches and 2 in the middle reaches, and the lower reaches of the river flow through the North China Plain without canyons. The canyon section of the main stream is 1,707 kilometers long, accounting for the total length of the main stream. Mangga Gorge - Duoshi Gorge - Maiduotang Gongma Gorge - Guancang Gorge - Lajia Gorge - Yehu Gorge - Lagan Gorge - Longyang Gorge - Ashgong Gorge - Songba Gorge - Lijia Gorge - Gongbo Gorge - Jishi Gorge - Sigou Gorge - Liujia Gorge - Niubi Gorge - Zhu Lama Gorge - Yanpan Gorge - Chaijia Gorge - Sangyuan Gorge - Daxia (Xiaxia) - Wujin Gorge - Hongshan South Gorge - Hongshan North Gorge - Black Mountain Gorge - Tiger Gorge - Qingtong - Qingtong - Jinshan Gorge - Jinyu Gorge (including Sanmenxia - Renjiadui - Bali Hutong - Xiaolangdi).

The main tributaries of the Yellow River include the Bai River, the Hei River, the Huangshui River, the Zuli River, the Qingshui River, the Dahei River, the Kuye River, the Wuding River, the Fen River, the Wei River, the Luo River, the Qin River, the Dawen River, etc.

The main lakes on the Yellow River are Zhaling Lake, Ngoling Lake, and Wuliangsuhai.

Sayings, proverbs:

Jumping into the Yellow River can not be washed, the Yellow River is rich in Ningxia, the richest is Wu Zhong, the Yellow River still has a clear day, how can people have no luck, the Yellow River in the world is rich in Ningxia, the heart of the Yellow River is not dead, and the coffin is not shed tears.

The Yellow River, the second largest river in China. It originates from the ancient Zonglie Basin at the northern foot of Bayankala Mountain on the Qinghai Plateau, meanders eastward, crosses the Loess Plateau and the Huanghuaihai Plain, and flows into the Bohai Sea. The total length of the main stream is 5,464 kilometers, and the water surface difference is 4,480 meters.

The total area of the basin is 10,000 square kilometers (including the area of the inflow area is 10,000 square kilometers).