Thulium

LANTHANIDE

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

Thulium is a chemical element with symbol Tm and atomic number 69. It is the thirteenth and antepenultimate (third-last) element in the lanthanide series. Like the other lanthanides, the most common oxidation state is +3, seen in its oxide, halides and other compounds.

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Quick Facts

Atomic Number 69

Period 6

Group 15

Phase Solid

Appearance silvery gray

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 Per Teodor Cleve

Named By Unknown

Physical Properties

Atomic Mass 168.934222

Density 9.32 g/L

Molar Heat 27.03 J/(mol·K)

Phase Transition (Melting & Boiling Points)

Thulium melts at 1818 K and boils at 2223 K.

Atomic Properties

Electron Config [Xe] 4f13 6s2

Electronegativity 1.25

Electron Affinity 99 kJ/mol

Ionization Energy 596.7 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.