Promethium

LANTHANIDE

Bohr Model: Electrons arranged in energy shells around the nucleus.

Promethium, originally prometheum, is a chemical element with the 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, a distinction shared with technetium. Chemically, promethium is a lanthanide, which forms salts when combined with other elements.

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Quick Facts

Atomic Number 61

Period 6

Group 7

Phase Solid

Appearance metallic

About Lanthanides

Lanthanides are shiny metallic elements with atomic numbers 57–71. They are often called 'rare-earth elements' and are used in magnets and lasers.

History

Discovered By Chien Shiung Wu

Named By Isotopes of promethium

Physical Properties

Atomic Mass 145

Density 7.26 g/L

Molar Heat N/A J/(mol·K)

Phase Transition (Melting & Boiling Points)

Promethium melts at 1315 K and boils at 3273 K.

Atomic Properties

Electron Config [Xe] 4f5 6s2

Electronegativity 1.13

Electron Affinity 12.45 kJ/mol

Ionization Energy 540 kJ/mol

Orbital Filling Diagram

This diagram visualizes electron configuration according to the Aufbau principle and Hund's rule. Boxes represent orbitals (s, p, d, f), while arrows indicate electrons with spin up or down. Electrons fill lower energy levels first and occupy orbitals singly before pairing.

Photograph

Source: Wikipedia

External Resources

Wikipedia PubChem Royal Society of Chemistry Periodic Videos (YouTube)

Study Guide

Atomic Number

The number of protons in the nucleus, which defines the element.

Atomic Mass

The average mass of an atom, including protons and neutrons.

Electronegativity

A measure of how strongly an atom attracts electrons in a bond.

Ionization Energy

The energy required to remove an electron from an atom.

Electron Config

The arrangement of electrons in the atom's energy shells.