Lanthanum
LanthanideAtomic Number: 57 • Atomic Mass: 138.9100 u • Period: 6 • Group: 3
Atomic Structure
Electron Configuration
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 5d¹The electron configuration represents the distribution of electrons in atomic orbitals, showing how they are arranged in energy levels and subshells.
Subatomic Particles
57
Positive charge
82
No charge
57
Negative charge
Atomic Number & Mass Number
The atomic number (57) represents the number of protons in the nucleus.
The mass number (139) is the sum of protons and neutrons in the nucleus.
Isotopes
Isotopes are variants of an element that have the same number of protons but different numbers of neutrons.
La-138
La-139
Stability & Half-Life
Half-Life Information
La-139 is stable, La-138 has half-life of 102 billion years
Half-life is the time required for half of the atoms of a radioactive isotope to decay.
Periodic Table Location
Period: 6
Group: 3
Category: Lanthanide
The period indicates the main energy level, while the group suggests similar chemical properties.