The key difference between actinides and lanthanides is that the actinides fill electrons to 5f sub-orbitals, whereas lanthanides fill electrons up to 4f sub-orbitals.
Lanthanides and actinides occur in two separate rows in the periodic table. Hence, both belong to the f block. It is because they have their outermost electrons in f orbitals. Therefore, we can name them as f block elements.
What are Actinides?
Actinides is a set of elements in the periodic table with the atomic numbers ranging from 90 to 103. Accordingly, there are 14 metal elements including the followings:
- thorium Th (Z=90)
- protactinium Pa (91)
- uranium U (92)
- neptunium Np (93)
- plutonium Pu (94)
- Americium Am (95)
- curium Cm (96)
- berkelium Bk (97)
- californium Cf (98)
- einsteinium Es (99)
- fermium Fm (100)
- mendelevium Md (101)
- a unit Ї 102
- lawrencium Lr (103).
We name them as f block elements; because their final electrons are in an f sub-orbital. All the actinides are unstable; therefore, all are radioactive. Since they are metals, they are highly electropositive. Moreover, they are dense metals, and numerous allotropes are present. These metals readily tarnish in the air and react with boiling water or dilute acid releasing hydrogen gas.
Like other metals, they can also form compounds with nonmetal elements. Furthermore, we can find actinides in the natural environment, though some are very rare. For instance, uranium and thorium are present as deposits, in Canada. Due to their radioactivity, most of the actinides are useful in nuclear energy production. We can produce actinide elements synthetically to use them for various purposes. Other than that, some of them are useful for medicinal purposes, mineral identification, neutron radiography, etc.
What are Lanthanides?
Lanthanides contain elements from atomic number 57 to 71. There are 15 metallic elements. These elements include the followings:
- lanthanum La (57)
- cerium Ce (58)
- Praseodymium Pr (59)
- neodymium Nd (60)
- promethium Pm (61)
- samarium Sm (62)
- Europium Eu (63)
- Gadolinium Gd (64)
- Terbium Tb (65)
- dysprosium Dy (66)
- Holmium Ho (67)
- yttrium Er (68)
- thulium Tm (69)
- ytterbium Yb (70)
- Lutetium Lu (71).
These belong to the f block in the periodic table; hence final electrons fill into the 4f sub-orbital. There, other sub-orbitals cover the 4f orbitals, and the chemistry of lanthanides differ due to the size of the atom. They show +3 oxidation state. Further, from left to right of a row in the periodic table, the size of +3 lanthanide ions decreases, and we call this as lanthanide contraction.
Moreover, lanthanides are silver colour metals, which react readily with oxygen in the air to produce their oxides. These are highly reactive, relatively soft metals with high melting points and boiling points. Also, they readily form ionic compounds with nonmetals. When reacting with dilute acid or water lanthanides produce hydrogen gas.
Apart from that, these elements have unpaired electrons (except lutetium), which are responsible for their paramagnetic properties. Moreover, we name them as rare earth metals due to the low abundance on earth surface. Although they are rare, there are lots of usages from these elements. Hence, they are useful as catalysts in glass production, petroleum, etc. Further, they are useful in magnets, phosphors, lamps, superconductors, optoelectronic applications, etc.
What is the Difference Between Actinides and Lanthanides?
Actinides is a set of elements in the periodic table with the atomic numbers ranging from 90 to 103 while lanthanides is a set of elements in the periodic table with atomic numbers 57 to 71. The key difference between actinides and lanthanides is that the actinides fill electrons to 5f sub-orbitals, whereas the lanthanides fill electrons up to 4f sub-orbitals. Moreover, all the actinides are radioactive, but lanthanides are not (except promethium). As another difference between actinides and lanthanides, we can say that the lanthanides show maximum oxidation state +4 whereas the actinides show +3, +4, +5, +6 and +7 oxidation states.
Below infographic presents a comparison summary of the difference between actinides and lanthanides.
Summary – Actinides vs Lanthanides
Actinides is a set of elements in the periodic table with the atomic numbers ranging from 90 to 103 while lanthanides is a set of elements in the periodic table with atomic numbers 57 to 71. Therefore, their key difference exists in their electron configuration. Hence, the key difference between actinides and lanthanides is that actinides fill electrons to 5f sub-orbitals, whereas lanthanides fill electrons up to 4f sub-orbitals.
1. Libretexts. “Lanthanides: Properties and Reactions.” Chemistry LibreTexts, National Science Foundation, 26 Nov. 2018. Available here
2. Libretexts. “The Actinides.” Chemistry LibreTexts, National Science Foundation, 26 Nov. 2018. Available here