Hydrogen is light in all elements. It is in the first place in the periodic table. There is only one electron outside the nucleus of oxygen. There are three isotopes of hydrogen, which mainly exist in the tissues of water, oil, coal, gas, and various organisms in a compound state. Its content in the earth's crust is expressed as a percentage of atoms, about 17.o%. Water contains 11% oxygen by weight, soil contains about 1.5%, and the main component is oxygen at an altitude of 100 kilometers, but the content in the atmosphere layer is very low. The air adjacent to the ground contains only a very small amount of hydrogen. The results of spectroscopic analysis show that the atmosphere of the sun and the planet contains about 81.75% hydrogen expressed as a percentage of atoms, and hydrogen is the most abundant element in the entire universe.
(1) Physical properties of oxygen
Under normal conditions, hydrogen is a colorless, odorless and odorless gas. It is lighter than air. It has been determined that under standard conditions (temperature 0°C and pressure of 101,325 kPa), the mass of 1 liter of hydrogen is 0.089 grams. Compared with the same volume of air, hydrogen is about 1/14 of the mass of air, and 4.38 times lighter than air. At 101,325 kPa, hydrogen can turn into a colorless liquid at 252.8 °C (20,2 K) and a snow-like solid at 259.2 °C (13.8 K). It is difficult to dissolve in water and liquefy. Such a light gas naturally has the greatest diffusion rate and high thermal conductivity, and its thermal conductivity is 7 times greater than that of air. Hydrogen is very soluble in water, while it is very soluble in nickel, palladium and molybdenum, and the palladium is soluble in one volume
Solve hundreds of volumes of hydrogen. Hydrogen is very permeable, and can pass through rubber and latex tubes at room temperature, and metal films such as palladium, nickel, and steel at high temperatures. Because hydrogen is highly permeable, when the steel is exposed to a certain temperature and pressure hydrogen, the atomic hydrogen permeating the crystal lattice of the steel causes embrittlement in the slow deformation. It reacts with carbon in the microscopic pores of steel to form methane. With the increase of methane production, the pores expand into cracks, which accelerates the migration of carbon in the microstructure, reduces the mechanical properties of the steel, and even causes damage to the material.
(2) Chemical properties of hydrogen
Hydrogen is stable at room temperature, but can chemically react with many substances under conditions such as ignition or heating.
1 Flammability of hydrogen
2 Reducing properties of hydrogen