What is At? Important knowledge about At.

Provide 5 examples [if any]

5. Application of At
   Present the applications of At in society, economy, medicine, manufacturing, engineering, environment, etc.

6. Safety when working with At
   Remind students about the safety rules when practicing chemistry with At.

For each specific chemical, the teacher can fill appropriate information into the above template. For example, if the chemical is iron (Fe), we can fill in as follows:

1. Definition of Fe
   1.1 Names
   1.1.1 Common name: Iron
   1.1.2 English name: Iron
   1.2. Atomic mass: 55.845
   1.3. Atomic weight: 55.845 amu
   1.3.1 Molecular structure: Iron is a chemical element so each molecule contains one iron atom.
   1.4 Ion structure: Iron typically forms Fe₂+ or Fe₃+ ions.

2. Properties of Fe
   2.1 Physical properties of Fe
   State: solid at room conditions
   Color: red-brown to black
   Smell: none
   PH level: not applicable
   2.2 Chemical properties of Fe: Iron reacts with Oxygen to form Iron (III) Oxide (Fe₂O₃).

3. Common chemical equations of Fe
   Metal Reaction: Fe + 2AgNO₃ -> 2Ag + Fe(NO₃)₂
   Acid reaction: Fe + 2HCl -> FeCl₂ + H₂

4. Preparation of Fe
   4.1 Laboratory preparation of Fe: not feasible
   4.2 Industrial preparation of Fe: Iron is usually prepared from iron ore in a blast furnace.

5. Application of Fe
   Iron has many applications in life, from construction, manufacturing, to medicine.

6. Safety when working with Fe
   Like all chemicals, when working with iron one must adhere to safety rules in the laboratory.