The periodic table of elements is a basic tool in chemistry, which is used to organize and classify elements. It consists of a series of chemical elements arranged according to certain rules. The periodic table of elements was discovered and put forward by Russian chemist Mendeleev in 1869. Its original version contains only a few elements, but with the progress of science, new elements are constantly discovered, and the periodic table of elements is gradually improved and expanded.
The periodic table of elements is arranged according to the atomic number of elements (that is, the number of protons in the nucleus). Each element has a unique atomic number, which indicates its position in the periodic table. The first line of the periodic table of elements is 1A group elements, also known as alkali metals; The second row is 2A group elements, namely alkaline earth metals; The third row is 3B to 8B group elements, which are called transition elements; Then there are elements with increasing electronegativity, called main group elements; Finally, elements with high electronegativity are called halogens and rare gases.
Elements in the periodic table can also be grouped according to their chemical properties. For example, elements like hydrogen and lithium are all in the first group, and they have similar chemical properties. This grouping can help us understand and predict the chemical reactions and properties between elements.
In addition to the basic element information, the periodic table of elements also provides many other important information. For example, each element has a chemical symbol to simplify the representation of the element. A chemical symbol consists of the first letter or letters of the Latin name of an element. For example, the chemical symbol of hydrogen is H, and the chemical symbol of oxygen is O.
The periodic table also provides the atomic mass of elements. Atomic mass refers to the mass of an atom of an element, usually expressed in standard atomic mass units. Through the atomic mass of an element, we can calculate the number of atoms contained in an element with a certain mass. The periodic table of elements also provides the periodic trend of elements. These trends include atomic radius, ionization energy and electronegativity. By studying these periodic laws, we can reveal the laws and relationships between elements.
The periodic table of elements is a tool for organizing and classifying chemical elements. It provides us with abundant element information and helps us to understand the relationship and chemical properties between elements. The periodic table of elements plays an important role in chemical research and teaching, and plays an important role in promoting the development of science.
Element position judgment
1, and the number of element periods is equal to the number of electron layers outside the nucleus.
2. The ordinal number of the main group element is equal to the outermost electron number.
3. To determine the number of families, we must first determine whether it is the main family or the sub-family. The method is to gradually subtract the number of elements in each period with the atomic number, and the final difference can be determined. From the first period to the fifth period, the last difference is less than or equal to 10, and the difference is 8,9, 10, which is the family number. When the difference is greater than 10, the family number is subtracted again and the final result is the family number.
Time difference of the 6th and 7th periods1:Ⅰ a, 2: Ⅱ a, 3~ 17: lanthanide or actinide, 8 ~ 21:negative 14, and 22 ~ 22.