Top 20 chemical elements

The first 20 chemical elements are hydrogen, helium, lithium, beryllium, boron, carbon, nitrogen, oxygen, fluorine, neon, sodium, magnesium, aluminum, silicon, phosphorus, sulfur, chlorine, argon, potassium and calcium.

1, hydrogen H: 1766, was discovered by British aristocrat henry cavendish (1731-1810).

2. Carbon C: 1796, British chemist Smithsonian Tennant (1761-15) found that diamonds are made up of carbon atoms.

3. Oxygen O: 177 1 year, found in priestley, England and Scheler, Sweden; China ancient scientist Ma and his discovery (controversial).

4. Sodium: 1807, discovered by British chemist David, was prepared by electrolysis.

5. Calcium Ca: 1808 was discovered by British chemist David and made by electrolysis.

Extended data:

Valence States of Elements in the Periodic Table of Chemical Elements

(1) Except 1 period, the highest positive valence of the second periodic element increased from alkali metal+1 to nitrogen element +5, the highest positive valence of other periodic elements increased from alkali metal+1 to +7, and the negative valence of nonmetallic elements increased from carbon group -4 to-/kl.

(2) The highest positive valence and the lowest negative valence of the same main group element are the same.

The melting point of simple materials in the periodic table of chemical elements.

(1) With the increase of atomic number of elements in the same period, the melting point of metal elements increases and the melting point of nonmetal elements decreases; (The melting point of subgroup reached the highest in VIB group, and then decreased in turn).

(2) In the same group of elements, from top to bottom, the melting point of metal elements decreases and the melting point of non-metal elements increases.

Metal properties of elements in the periodic table of chemical elements

(1) In the same period, the metallic properties of elements decrease from left to right, while the nonmetallic properties increase;

(2) The metallicity of the elements of the same main group increases from top to bottom, while the nonmetal decreases.

Baidu Encyclopedia-Periodic Table of Elements