Atomic cluster

[yuán zǐ tuán]

Chemical terminology

Collection

zero Useful+1

zero

This entry is made by Compilation and application of scientific encyclopedia entries of "Science Popularization China" to examine.

The atomic group refers to the atomic group participating in the reaction as a whole in the chemical reaction. The atomic group is molecule Part of. In three or more Element composition The molecule of a compound often contains some kind of atomic group. Charged atomic clusters are also called roots, such as Hydroxyl radical OH⁻、 Nitrate NO₃⁻ 、 Carbonate CO₃²⁻，、 Sulfate radical SO₄²⁻、 Chlorate ClO three - 、 Phosphate radical PO₄³⁻、 Bicarbonate HCO₃⁻、 Ammonium radical NH ₄+etc.

Chinese name: Atomic cluster
Foreign name: Atomic group

Alias: root 、 Group
Discipline: Chemistry

catalog

Basic Introduction

Announce

edit

Charged atomic clusters are also called roots or Group , such as Hydroxyl radical OH - 、 Nitrate NO3 - 、 Carbonate CO three 2- ，、 Sulfate radical SO four 2- 、 Chlorate ClO three - 、 Phosphate radical PO four 3- 、 Bicarbonate HCO three - 、 Ammonium radical NH four + Etc. It is worth noting that: atom Groups cannot exist independently, but are only a part of compounds. In the solution, the atomic group participates in the reaction as a whole. Various atomic groups have their own characteristic reactions, such as CO three 2- Change into CO2, SO when encountering acid four 2- Meet Ba 2+ Produce white precipitate insoluble in dilute nitric acid, OH - Make phenolphthalein test solution turn red, etc. The existence of roots can be tested by characteristic reaction. Pay attention to distinguishing manganese oxide MnO four 2- And permanganate MnO four - , both have the same composition, but the manganese Valence Different, so Root valence Different, manganese in manganate is+6, and manganese in permanganate is+7. There are also Metaphosphate Root PO three - And phosphite PO three 3- The former is+5 and the latter is+3. The valence of an atomic group is equal to the algebraic sum of the valence of the elements in the root^[1] 。

characteristic

Announce

edit

Atomic cluster Its unique properties are due to its structural characteristics. Because of its small size, the proportion of atoms on the surface is very high. The geometry, spin state and inter atomic force of surface atoms are completely different from those of atoms in the body phase. The properties of materials are closely related to the surface properties of internal units. For example, just by adjusting the size of the cluster, the material properties are very different. The cluster with 10 iron atoms is 1000 times more effective than the cluster with 17 iron atoms in catalyzing ammonia synthesis^[2] 。

Another effect that comes with size is the quantum effect. The study of atomic clusters has proved that many quantum mechanics The hypothesis and prediction of the new model proposed numerous more interesting new problems. For example, in the polyhedron composed of pure metal atoms Cluster Medium, only when Atomic number Yes“ Magic number Series ", the structure is stable and will not be destroyed even when heated to liquid state. The same "magic number series" Periodic law of elements China has long been known, but its theoretical explanation is still inconclusive.

The scientific research of clusters is in the booming stage. In addition to the great theoretical significance, the practical application of atomic clusters in sound, electricity, light, magnetism and other aspects is the direction of people's efforts.

Pay attention to understanding

Announce

edit

(1) An atomic group is a part of a molecule. In three or more Element composition In the compound of^[3] 。

(2) The atomic group does not remain unchanged in any chemical reaction. In some chemical reactions, the atomic group will change, for example, the chlorate radical in potassium chlorate will change in the reaction.

(3) The atomic group is usually called "root" or "root ion". When writing the symbol of atomic group, the charge it carries should be noted, such as ClO three - 、SO four 2- 、OH - 、NH four + Wait, don't treat the symbol of atomic group as chemical formula , such as sulfate radical (SO four 2- ）Mistaken for Sulfur tetroxide 。

Corresponding substances

Announce

edit

Acids and salts

In atomic clusters^[4] Most of them are acid radicals. If it is to be changed into corresponding acid, it is generally Acid radical A corresponding number of hydrogen atoms are added before it. If nitrate NO3 turns into nitric acid, it is HNO3, and sulfate SO42 turns into sulfuric acid, it is H2SO4. The same is true for salt, except that metal or ammonium is added before acid radical.

Organic acid radical becomes organic acid or corresponding salt. When writing chemical formula, note that hydrogen or metal is written in front of acid radical.

alkali

Alkali is the hydroxyl OH - Add metal elements before.

ammonia

Ammonium is special. Since it has+1 valence, the corresponding substance is changed into ammonia NH by removing one hydrogen three

Cyanogen

Cyanide is also special. Cyanogen is CN - , and the chemical formula of cyanide is (CN) two