The first twenty elements and letters of the periodic table.

The first twenty elements and letters:

Hydrogen (H), helium (He), lithium (Li), beryllium (Be), boron (B), carbon (C) ), nitrogen (N), oxygen (O), fluorine (F), neon (Ne), sodium (Na), magnesium (Mg), aluminum (Al), silicon (Si), sulfur (S), chlorine (Cl) ), argon (Ar), potassium (K), calcium (Ca).

Russian chemist Dmitri Mendeleev invented this periodic table (the first generation periodic table of elements) in 1869.

The list is generally rectangular, with spaces left in some element cycles so that elements with similar properties can be grouped into the same group, such as alkali metal elements, alkaline earth metals, halogen elements, rare gases, etc. This makes the elements in the periodic table divided into seven main groups, seven sub-groups, Group VIII and Group 0. Extended information

Using the periodic table, Mendeleev successfully predicted the properties of elements that had not yet been discovered at the time (gallium, scandium, and germanium). In 1913, the British scientist Moselle used cathode rays to hit metals to produce X-rays. He found that the greater the atomic number, the higher the frequency of Positive charge (i.e. proton number or atomic number) arrangement.

The position of an element in the periodic table not only reflects the atomic structure of the element, but also shows the gradient of the element's properties and the intrinsic relationship between the elements. It constitutes a complete system and is known as one of the important milestones in the development of chemistry.

Baidu Encyclopedia - Periodic Table of Elements