Lanthanum

LANTHANIDE

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

Lanthanum is a soft, ductile, silvery-white metallic chemical element with symbol La and atomic number 57. It tarnishes rapidly when exposed to air and is soft enough to be cut with a knife. It gave its name to the lanthanide series, a group of 15 similar elements between lanthanum and lutetium in the periodic table:it is also sometimes considered the first element of the 6th-period transition metals.

← PreviousBarium Next →Cerium

Quick Facts

Atomic Number 57

Period 6

Group 3

Phase Solid

Appearance silvery white

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 Carl Gustaf Mosander

Named By Unknown

Physical Properties

Atomic Mass 138.905477

Density 6.162 g/L

Molar Heat 27.11 J/(mol·K)

Phase Transition (Melting & Boiling Points)

Lanthanum melts at 1193 K and boils at 3737 K.

Atomic Properties

Electron Config [Xe] 5d16s2

Electronegativity 1.1

Electron Affinity 53 kJ/mol

Ionization Energy 538.1 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.