Beryllium is a chemical element with the symbol Be and atomic number 4. It is a lightweight, strong metal that is primarily used in aerospace and military applications due to its excellent thermal and electrical conductivity. Beryllium is also found in some alloys and is used in the production of X-ray equipment and nuclear reactors. This element is relatively rare in the Earth's crust and is typically extracted from minerals such as bertrandite and beryl. While beryllium has useful properties, it can be toxic if inhaled as dust or fumes, making safety precautions essential when handling it.