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Lanthanum Element in Periodic Table | Atomic Number Atomic Mass


Lanthanum Element:

Lanthanum is the first chemical element in the series of fifteen elements, called Lanthanide series in the periodic table. Lanthanum is an element with atomic number as 57 and is represented by the symbol La. It is a silvery-white metal and malleable. It is a soft metal so that it can be cut with a knife. It is the first element of the 6th period containing transition elements. The Lanthanide series starts with the La  and ends with the chemical element Lutetium.

Although La is included as the first element in the f-block elements, it does not have any electrons in 4f-orbital, ironically. Hence, it displays very weak paramagnetic character and the last two elements in the lanthanide series Ytterbium and Lutetium display a very strong paramagnetic character due to the presence of completely 4f-orbitals. The softness of lanthanides decreases with increase in atomic number. The oxidation number of Lanthanum is +3 and it forms readily oxides on reacting with oxygen. Lanthanum oxide, La2O3, exhibits similar basic properties of calcium oxide, CaO. La  reacts slowly with water to form lanthanum hydroxide, La (OH)3. Lanthanum hydroxide reacts with atmospheric carbon dioxide to form its basic carbonate.

La exists in two naturally occurring isotopic forms, 138La and 139La, out of which the latter is the most abundant with its 99.9% presence.

Uses Of Lanthanum Element:

  • Lanthanum is used as in mischmetal alloy, which is in turn used as a flint in cigarette lighters. La when present in rare earth metal compounds is used in carbon lighting applications such as studio lighting and cinema projection. Compounds of  La are also used in high quality glasses/lenses. Lanthanum is used in manufacture of optical fibre material called ZBLAN; the acronym ZBLAN is derived from the first letters of symbols of the component chemicals Zirconium, Barium, Lanthanum, Aluminum and Sodium.


Lanthanum and its compounds are poisonous in high concentrations. Hence, caution should be exercised while handling them.


Lanthanum Element Information:

Discovery year: 1838

Discovered by: Carl Gustaf Mosander

Atomic number: 57

Relative atomic mass: 138.905 

Electron configuration: [Xe] 5d1 6s2

Block: d-block

Other elements in the same block:

Scandium, Titanium, Vanadium, Chromium, Manganese, Iron, Cobalt, Nickel, Copper, Zinc, Yttrium, Zirconium, Niobium, Molybdenum, Technetium, Ruthenium, Rhodium, Palladium, Silver, Cadmium, Hafnium, Tantalum, Tungsten, Rhenium, Osmium, Iridium, Platinum, Gold, Mercury, Actinium, Rutherfordium, Dubnium, Seaborgium, Bohrium, Hassium, Meitnerium, Darmstadtium, Roentgenium and  Copernicium are the elements in the same block.

Period: period 6

Other elements in the same period:

Caesium, Barium, Cerium, Praseodymium, Neodymium, Promethium, Samarium, Europium, Gadolinium, Terbium, Dysprosium, Holmium, Erbium, Thulium, Ytterbium, Lutetium, Hafnium, Tantalum, Tungsten, Rhenium, Osmium, Iridium, Platinum, Gold, Mercury, Thallium, Lead, Bismuth, Polonium, Astatine and Radon

Group: group 3

Other elements in the same group:

Scandium, Yttrium and Actinium are the same group elements

Other elements in the same orbital:

Cerium, Praseodymium, Neodymium, Promethium, Samarium, Europium, Gadolinium, Terbium, Dysprosium, Holmium, Erbium, Thulium, Ytterbium and Lutetium are the elements in the same orbital.

Allotropes: none

Key isotopes: 139La 

Melting point: 920°C, 1688°F, 1193 K

Boiling point: 3464°C, 6267°F, 3737 K

Element category:  lanthanide

Density (g cm−3): 6.15

CAS number: 7439-91-0

Color: silvery white

You can know detailed information for each element,

Hydrogen, HeliumLithiumBerylliumBoronCarbonNitrogenOxygenFluorine,  Neon , SodiumMagnesiumAluminiumSiliconPhosphorusSulfurChlorineArgon, PotassiumCalciumScandiumTitaniumVanadiumChromiumManganeseIronCobaltNickelCopperZincGalliumGermaniumArsenicSeleniumBromine, Krypton,  Rubidium, StrontiumYttriumZirconiumNiobiumMolybdenumTechnetiumRutheniumRhodiumPalladiumSilverCadmiumIndiumTinAntimonyTelluriumIodine, Xenon,  Caesium, BariumLanthanum,  CeriumPraseodymiumNeodymiumPromethiumSamariumEuropiumGadoliniumTerbiumDysprosiumHolmiumErbiumThuliumYtterbiumLutetiumHafniumTantalumTungstenRheniumOsmiumIridiumPlatinumGoldMercuryThalliumLeadBismuthPoloniumAstatine, Radon,  Francium, RadiumActiniumThoriumProtactiniumUraniumNeptuniumPlutoniumAmericiumCuriumBerkeliumCaliforniumEinsteiniumFermiumMendeleviumNobeliumLawrenciumRutherfordiumDubniumSeaborgiumBohriumHassiumMeitneriumDarmstadtiumRoentgeniumCoperniciumNihoniumFleroviumMoscoviumLivermoriumTennessine, Oganesson.

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