Make your own free website on


Information valid for La-139 unless otherwise noted

Basic Information

Symbol: La
Atomic Number: 57
Mass: 138.9055
Melting Point: 920.0 C
Boiling Point: 3469.0 C
Number of Protons/Electrons: 57
Number of Neutrons: 82
Classification: Rare Earth
Crystal Structure: Hexagonal
Density @ 293 K: 6.7 g/cm3
Color: white

Atomic Structure

[Bohr Model of Lanthanum]
Number of Energy Levels: 6

  1. First Energy Level: 2
    Second Energy Level: 8
    Third Energy Level: 18
    Fourth Energy Level: 18
    Fifth Energy Level: 9
    Sixth Energy Level: 2


Isotope Half Life
La-134 6.5 minutes
La-137 6000.0 years
La-138 1.05E10 years
La-139 Stable
La-140 1.67 days
La-141 3.9 hours
La-142 1.54 minutes


Date of Discovery: 1839
Discoverer: Carl Mosander
Name Origin: From the Greek word lanthaneis (to lie hidden)
Uses: expensive camera lenses
Obtained From: monazite, bastnasite