Atomic Number
61
Element 61
Promethium (Pm)
Promethium is a chemical element with symbol Pm and atomic number 61. All of its isotopes are radioactive; it is one of only two such elements that are followed in the periodic table by elements with stable forms.
Atomic Mass
145 u
Category
Lanthanide
Period
6
Group
Lanthanide series
Phase
solid
Density
7.26 g/cm3
Electron Shells
2, 8, 18, 23, 8, 2
Atomic Structure
Protons: 61. Electrons: 61. Neutrons: Varies by isotope.
Electron configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f⁵
Why Promethium Matters
Promethium helps connect atomic number 61, lanthanide behavior, period 6 trends, and electron shell structure. Its solid phase, atomic mass of 145 u, and electron configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f⁵ make it useful for comparing bonding patterns across the periodic table.
Discovery and Occurrence
Promethium was discovered 1945 by Jacob A. Marinsky, Lawrence E. Glendenin, Charles D. Coryell. Promethium is a chemical element with symbol Pm and atomic number 61. All of its isotopes are radioactive; it is one of only two such elements that are followed in the periodic table by elements with stable forms.
Safety and Handling Context
Promethium has radioactive isotopes or is commonly discussed with radioactive materials. Use this page as an educational reference; real samples require qualified supervision and controlled handling.
Related Elements
Frequently Asked Questions
- What is the atomic number of Promethium?
- Promethium has atomic number 61, which means a neutral atom has 61 protons and 61 electrons.
- What is the chemical symbol for Promethium?
- The chemical symbol for Promethium is Pm.
- What category is Promethium in?
- Promethium is classified as a lanthanide and sits in period 6 of the periodic table.
Explore Promethium in 3D
Use the interactive table above to rotate atomic models, compare periodic trends, and move from Promethium to neighboring elements without losing your place.