Periodic Table is an atom from small to large chemical elements sorted list of the ordinal number. The list is generally rectangular, with spaces in some elements of the cycle, so that elements with similar properties belong to the same family, such as alkali metals, alkaline earth metals, halogens, rare gases, and so on.

This causes the elements in the periodic table to be partitioned and divided into seven main groups, seven sub-groups, VIII groups, and 0 groups. Because the periodic table accurately predicts the properties of various elements and their relationships, it is widely used in chemistry and other scientific fields as a useful framework for analyzing chemical behavior.

Russian chemist Mendeleev (Dmitri Mendeleev) in the invention Periodic Table 1869, since been proposed various types of the Periodic Table was no less than 170 species, can be summarized in Short table (as in Mendeleev Representative), long form (represented by Werner), special table (represented by Porta); plane spiral and circular (represented by Damboff); Lacey’s conical cylindrical table is representative).

Development path

Modern chemistry periodic law is the 1869 Russian scientist Mendeleev (Dmitri Mendeleev) first created, he will be 63 elements known at that time in accordance with the relative atomic mass and size are arranged in the form of a table, to have similar chemical properties.


The elements are placed in the same column and are made into the prototype of the periodic table. After many years of revision, it has become a contemporary periodic table. In the periodic table, elements are arranged in the atomic order of the elements, with the smallest ranking being the first. A horizontal row in the table is called a cycle, and a column is called a family.

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The atomic radii decrease from left to right, increasing from top to bottom.

In the chemistry textbooks and dictionaries, there is a “The Periodic Table“. This table reveals the secrets of the material world and unifies elements that appear to be unrelated to each other to form a completely natural system.


Its invention, is the modern history of chemistry a pioneering work for the promotion of the development of chemistry, played a huge role. When you see this watch, people will think of its earliest inventor, Mendeleev. In 1869, the Russian chemist Mendeleev arranged the first elemental periodic table according to the relative atomic mass from small to large and placed the chemically similar elements in the same longitudinal direction.

The periodic table of elements reveals the intrinsic link between chemical elements, making it a complete system and one of the important milestones in the history of chemical development. With the development of science, the vacancies left by unknown elements in the periodic table are filled.

When the mystery of the atomic structure is discovered, the arrangement is based on the number of protons (external electrons or nuclear charge) changed from the relative atomic mass to the atom, forming the current periodic table of elements.

The atomic number is obtained by numbering the elements in the order they are in the periodic table. The atomic number has the following relationship with the atomic structure of the element:

Proton number = atomic number = extranuclear electron number = nuclear charge number

Using the periodic table, Mendeleev successfully predicted the characteristics of the elements (gallium, germanium, and antimony) that were not discovered at the time.

Periodic Table

In 1913, the British scientist Mosler used the cathode ray to strike the metal to produce the ray X. It was found that the larger the atomic order, the higher the frequency of the X-ray.

Therefore, he believed that the positive charge of the nucleus determines the chemical nature of the element and the element is in accordance with the nucleus.

Positively charged (i.e., a proton numbers or atomic order) arrangement. Later, after several years of revision by many scientists, a contemporary periodic table was formed.

Arrange elements in order of relative atomic mass from small to large, and place chemically similar elements in a column. Each element has a sequence number that is exactly equal to the number of protons in the atom of the element’s atom.

This sequence number is called the atomic number. In the periodic table, elements are arranged in the atomic order of the elements, with the smallest ranking being the first. A horizontal row in the table is called a cycle, and a column is called a family.

The extranuclear electron arrangement and properties of the atom have obvious regularity. The scientists arrange the elements in the same order by increasing the atomic number. The elements with the same number of electron layers are placed in the same row, and the elements with the same outermost electron number are placed in the same column.

The periodic table has 7 cycles and 16 families. Each traverse is called a cycle, and each trajectory is called a family (the VIII family contains three columns).

These 7 cycles can be divided into short periods (1, 2, and 3) and long periods (4, 5, 6, and 7). There are a total of 16 families, counting each family from left to right (except for Group VIII). For example, hydrogen belongs to the group IA element and belongs to the group 0 element.

The position of an element in the periodic table not only reflects the atomic structure of the element but also shows the law of the evolution of the element’s nature and the intrinsic relationship between the elements. Making it a complete system is called one of the important milestones in chemical development.

In the same cycle, from left to right, the number of electron layers outside the elemental core is the same, the number of outermost electrons increases in turn, and the atomic radius decreases (except for the zero-member elements).

The ability to lose electrons is gradually weakened, the ability to acquire electrons is gradually enhanced, the metallicity is gradually weakened, and the non-metallicity is gradually enhanced.

The highest positive oxidation number of an element increases from left to right (except for no positive price), and the lowest negative oxidation number increases from left to right (except for the first period, except for the O and F elements of the second period).

In the same family, from top to bottom, the number of outermost electrons is the same, the number of extranuclear electron layers is gradually increasing, the atomic radius is increased, the atomic number is increasing, the elemental metality is increasing, and the non-metallicity is decreasing.

Periodic Table_lanthanides

The periodic table of elements is of great significance, and scientists use it to find new elements and compounds.

On December 31, 2015, the US Science News biweekly website published a report entitled “The Four Elements Get Permanent Seats on the Periodic Table of the Elements”.

The International Union of Pure and Applied Chemistry (IUPAC) announced that the Russian and American research teams have obtained sufficient evidence to prove that they have discovered elements 115, 117 and 118.

In addition, the federation has recognized the discovery of element 113 by researchers at the Japan Institute of Physical Chemistry. The two research teams synthesized the above four elements by colliding the lighter nucleus and tracking the decay of the radioactive super-heavy elements produced thereafter.

IUPAC executive director Lynn Sabi said that a report on identifying new elements will be released in early 2016. Official recognition of these elements means that their discoverers have the right to name and design symbols. Element 113 will be the first element discovered and named by Asians. It was officially named Nihonium in June 2016, symbol Nh.

On December 30, 2015, the International Union of Pure and Applied Chemistry announced the existence of elements 113, 115, 117, 118, which will be named by scientists from Japan, Russia, and the United States. IUPAC officially announced that the Periodic Table of the Elements has added four new elements.

On June 8, 2016, the International Union of Pure and Applied Chemistry announced the nomination of synthetic chemical elements No. 113 (abbreviated as Nh), No. 115 (Mc), No. 117 (Ts) and No. 118 (Og) as new chemical Element.

Element naming

Many people have noticed that the last few elements of the periodic table often start with Uu. In fact, this is just a temporary naming convention called the IUPAC element system nomenclature.

In this nomenclature, a temporary Western text name is assigned to an undiscovered element and an element that has been discovered but not yet officially named, and a surrogate element symbol is specified, using a Latin numeric header named after the atomic order of the element.

This rule is simple and easy to use, and it solves the vicious competition problem of pre-named newly discovered elements, which makes the naming of new elements.

For example, ununquadium is a combination of four roots: UN (a) -UN (a) -qua (tetra)-ium (element), which means “element 114”. Element 114 is named flerovium (Fl) to commemorate the Soviet atomic physicist Georgy Flyorov (1913-1990); and ununhexium is UN (a) – UN (a)-hex (six)) – ium (element) four words are combined to represent “element 116”. Element 116 is called livermorium (Lv) and is named after the city of Livermore, where the laboratory is located.

Positional relationship

Atomic radius

(1) Except for the first cycle, the atomic radii of other periodic elements (except rare gas elements) decrease as the atomic number increases;

(2) The elements of the same family increase from the top to the bottom, as the number of electron layers increases, and the atomic radius increases. (Except for the sub-family between the five and six weeks)

Elemental valence

(1) Except for the first cycle, the same period from left to right, the highest positive price of the second periodic element increases from alkali metal +1 to nitrogen element +5 (no normal price of fluorine, no highest positive price of oxygen), other periodic elements The highest positive price is increased from alkali metal +1 to +7, and the non-metallic element negative price is increased from carbon family-4 to -1.

(2) The highest normal price and the lowest negative price of the elements of the same main family are the same. (Except VIA, VIIA, and 0)

Elemental melting point

(1) As the atomic number of the same period increases with the atomic number, the melting point of the elemental metal element increases, and the melting point of the non- metal element decreases; (the melting point of the sub-group reaches the highest in the VIB family, and then decreases in turn).

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(2) From the top to the bottom of the same family element, the melting point of the elemental metal element decreases, and the melting point of the non-metal element increases. (Sub-family irregular)

Metallicity of the element

(1) From left to right element of the same cycle metallic decreasing, non-metallic increment;

(2) The same main group element increases in metality from top to bottom, and the non-metallicity decreases.

Hydrate acidity and alkalinity of the highest valence oxide

The stronger the metallicity of the element, the stronger the basicity of the hydrate of the highest valence oxide; the stronger the non-metallicity of the element, the stronger the acidity of the hydrate of the highest valence oxide. (Except F and O).

Non-metallic gas state

The stronger the element is non-metallic, the more stable the gaseous hydride is. The stronger the non-metallicity of the non-metallic elements in the same period, the stronger the acidity of the aqueous solution of the gaseous hydride is.

The stronger the non-metallicity of the non-metallic elements of the main group, the weaker the acidity of the aqueous solution of the gaseous hydride.

Elemental oxidation

The stronger the mentality of the general element, the stronger the reduction of the elemental substance, and the weaker the oxygen ion oxidation of the oxide; the stronger the non-metallicity of the element, the stronger the oxidation of the elemental substance, and the reduction of the monoatomic anion. The weaker.

Element position inference

  1. The number of element periods is equal to the number of layers of extranuclear electrons;
  2. The ordinal number of the main family element is equal to the outermost electron number;

3, determine the number of families should first determine whether it is the main or sub-family, the method is to use the atomic number to gradually subtract the number of elements of each cycle, which can be determined by the final difference. In the first to fifth cycles, the last difference is less than or equal to 10, and the difference is the family number. When the difference is 8, 9, 10, it is VIII.

When the difference is greater than 10, then 10 is subtracted. The final result is the family number. In the sixth and seventh cycles, the difference is 1: I A, the difference is 2: IIA, the difference is 3~17: The difference is between 18 and 21: minus 14, difference the number is 22~24: VIII, the difference is greater than 25: minus 24, corresponding to the main family.

Periodic Table_Actinides

According to the type of elements contained in each cycle, the atomic number is subtracted from the number of elements contained in each cycle. When the result is “0”, it is a zero family; when it is a positive number, it is from left to right in the periodic table.

The wales of the number, if “2”, are the second ordinate from the left to the right in the periodic table, that is, the IIA group; when it is negative, the main family ordinal number is 8+. Therefore, the number of elements of each period should be memorized, that is, 2, 8, 8, 18, 18, 32, 32.

For example, the position of element 1114 in the periodic table is 114-2-8-8-18-18-32-32=-4, 8+ (-4) =4, which is the seventh cycle, group IVA. The position of element 275 in the periodic table is 75-2-8-8-18-18=21, 21-14=7, which is the sixth cycle, the VIIB family.

Rare gas element

Rare gases, also known as inert gases, are chemically stable and do not readily react chemically with other materials. Stable rare gases are: Helium (He) Neon (Ne) Argon (Ar) Krypton (Kr) Xenon (Xe) Radon (Rn)

Keep in mind the atomic number of rare gas elements: 2, 10, 18, 36, 54, 86. Position the element of a known atomic number by the location of the rare gas.

For example, to infer the position of element No. 33, because it is between 18 and 36, it must be in the fourth cycle, from the 36th to the left, should be in the VA family.

Secondary periodicity

The Periodic Table, p-block variation from top to bottom is not a strictly increasing curve, but a sawtooth-shaped curve. There are two inflection points on the curve: the second cycle and the fourth cycle. According to the calculation of the relativistic effect, the third inflection point will appear in the sixth cycle.

Irregularity of the second cycle

The cause is that the inner electrons in the second period are small (only 1s 2), and the atomic radius is extremely small. Therefore, the manner and type of elements in the second period are greatly different from the latter periods.

For example, nitrogen-based elements (VA) have been produced in the third to sixth cycles of pentachloride, but NF 5 does not exist, not to mention molecules such as NCl 5. Another example is the difference in the maximum coordination number of carbon and silicon, resulting in a difference in the crystal structure of carbon dioxide and silicon dioxide.

Irregularity of the fourth cycle

The p-region element of the fourth cycle has just passed through the d-region, so the atomic radius does not change much compared to the third cycle of the same family. Therefore, many compounds in the fourth cycle are relatively unstable.

For example, HClO 4 and HIO 4 were prepared very early, but HBrO 4 was produced in 1967, and the oxidizing property is perhalogenated acid (except for high fluoric acid, The strongest due to thermodynamic instability.

Irregularity in the sixth cycle (6s 2 inert electron pair effect)

In the sixth period, the atomic radius of the element is too large, and the 6s electron cloud has a large interval, which is difficult to form a bond. Except that Tl (III) is more stable, the elements of the p-zone of the sixth cycle are hard to show the family price. For example, Bi 2 O 3 is much less reductive than Sb 2 O 3, Bi 2 O 5 is much more oxidizing than Sb 2 O 3, and Po (VI) and At (VII) are not expected to exist.

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