Halogens are a group of non-metallic elements that are located in group A in the periodic table. Halogens include elements such as fluorine, chlorine, bromine, iodine, astatine, etc., and their state in nature is usually gaseous or liquid, with the exception of astatine. Halogen properties exhibit a distinct degradation, which is manifested not only in physical properties but also in chemical properties. From the physical properties, with the increase of atomic number, the color of halogen gradually deepens, from light yellow-green to dark reddish-brown to purple-black, and its melting and boiling point gradually increases, and the density gradually increases. In addition, the greater the atomic number of a halogen, the greater the relative molecular mass of its elemental matter, and the greater the intermolecular van der Waals force, so its solubility is smaller. This degraduality of physical properties helps us to better understand and grasp the properties and uses of halogen elements. From the chemical point of view, halogen elements have strong oxidation, and with the increase of atomic number, the oxidation gradually weakens. Halogen elements can react with many substances, such as metals, non-metals, water, alkalis, etc. In halogen mutuals, the oxidation of halogens is reduced due to the delocalization of electrons and the conjugation effect. In addition, halogens can form a variety of compounds such as oxyacids and oxygenates, which are also progressively variable in nature.
1) It is becoming more and more difficult to combine with H2, the stability of the hydride produced is getting worse and worse, the acidity of its aqueous solution is getting stronger and stronger, and its melting and boiling point is gradually increasing.
2) Reacting with H2O is getting harder and less reactive.
3) It is becoming more and more difficult to react with metals, F2, Cl2, Br2 react with valence metals to form ** compounds, and I2 reacts with variable metals to form low-valence compounds.
Fluorine is the most reactive non-metallic element, and it reacts with almost all elements; Chlorine is a yellowish-green gas with a strong pungent odor; Bromine is a toxic, dark reddish-brown liquid that is highly volatile and corrosive; Iodine, on the other hand, is a purple-black solid with sublimating properties. These different chemistries make halogens widely used in industry, agriculture, medicine and other fields. Halogens and compounds are also dangerous. For example, fluorine gas is highly toxic and corrosive, while chlorine gas is easy to form toxic compounds such as ***; Compounds of bromine and iodine are also toxic and corrosive. Therefore, appropriate safety measures need to be taken when using halogen elements and compounds. The degraduality of halogen properties is manifested in physical and chemical properties. Understanding the degradability of halogens helps us better understand their properties and application areas. At the same time, safety concerns need to be taken into account when using halogens and compounds. With the continuous development of science and technology and the in-depth research, the application field of halogen will be more extensive and deeper.