La

Lanthanum (La) is a soft, silvery rare-earth metal belonging to the lanthanide series, characterized by high reactivity and strong affinity for oxygen and other nonmetals. It is primarily used in alloy systems—particularly in nickel-metal hydride batteries, steel desulfurization, and optical glass applications—where its ability to enhance strength, workability, and optical properties makes it valuable despite requiring careful handling due to its reactivity. Engineers select lanthanum-containing materials when corrosion resistance, hydrogen storage capacity, or refractive index tuning is critical, though cost and processing complexity typically limit its use to high-performance and specialty applications.