Overview
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F block elements of the periodic table consist of Lanthanide and Actinide Series. The f block appears as a footnote in a standard 18-column table but is located at the centre-left of a 32-column full-width table. In this article, we will learn about f blocks in detail along with their Electronic Configuration, Occurrence, Physical properties, and Chemical Properties.
Also read about the blocks of the periodic table here.
The elements in which the differentiating electron enters into (n–2) f orbital are known as f block elements. They are also called inner transition elements, due to their position and properties. They belong to the third group of the periodic table. There are two series of f-block elements, 4f series (lanthanoid) and 5f series (actinoid). f0, f7, f14 electronic configurations achieve extra stability due to empty, half-filled and completely filled orbitals respectively.
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While these elements are generally not considered part of any group, some authors consider them to be part of group 3. They are sometimes called inner transition metals because they provide a transition between the s-block and d-block in the 6th and 7th row (period), in the same way that the d-block transition metals provide a transitional bridge between the s-block and p-block in the 4th and 5th rows.
The f-block elements come in two series, in periods 6 and 7. All are metals. The f-orbital electrons are less active in the chemistry of the period 6 f-block elements, although they do make some contribution: these are rather similar to each other.
With one 5d and two 6s electrons, lanthanum is the first element in the third transition series. Cerium comes next; it still has two 6s electrons but has two in the 4f orbitals and none in the 5d orbitals. There are seven different 4f orbitals, and each one can hold two electrons with opposing spins.
From cerium to lutetium, the atoms have two to fourteen electrons in 4f- orbitals, respectively. Although lanthanum itself doesn’t have any 4f electrons, it is common to place it in this series together with the other elements that make up the first inner transition series known as lanthanides.
The general valence shell electronic configuration of lanthanides
[X e] 4 f^{0,2} \text { to } 145 d^{0 \text { to } 16 s^2}
Lanthenide series (4f-block elements)
Atomic Number |
Symbol |
Name |
Electronic Configuration |
57 |
La |
Lanthanum |
[Xe] 5d¹ 6s² |
58 |
Ce |
Cerium |
[Xe] 4f¹ 5d¹ 6s² |
59 |
Pr |
Praseodymium |
[Xe] 4f³ 6s² |
60 |
Nd |
Neodymium |
[Xe] 4f⁴ 6s² |
61 |
Pm |
Promethium |
[Xe] 4f⁵ 6s² |
62 |
Sm |
Samarium |
[Xe] 4f⁶ 6s² |
63 |
Eu |
Europium |
[Xe] 4f⁷ 6s² |
64 |
Gd |
Gadolinium |
[Xe] 4f⁷ 5d¹ 6s² |
65 |
Tb |
Terbium |
[Xe] 4f⁹ 6s² |
66 |
Dy |
Dysprosium |
[Xe] 4f¹⁰ 6s² |
67 |
Ho |
Holmium |
[Xe] 4f¹¹ 6s² |
68 |
Er |
Erbium |
[Xe] 4f¹² 6s² |
69 |
Tm |
Thulium |
[Xe] 4f¹³ 6s² |
70 |
Yb |
Ytterbium |
[Xe] 4f¹⁴ 6s² |
71 |
Lu |
Lutetium |
[Xe] 4f¹⁴ 5d¹ 6s² |
The second series of 5f block chemical elements results from the filling of 5f-orbital. Actinides in f block consist of chemical elements like thorium to lawrencium with atomic numbers 90 to 103.
The general electronic configuration of 5f-block elements or actinides is
[Rn] 5f¹–¹⁴ 6d⁰–¹ 7s²
Actinides (5f-block Elements)
Atomic Number |
Symbol |
Name |
Electronic Configuration |
90 |
Th |
Thorium |
[Rn] 6d² 7s² |
91 |
Pa |
Protactinium |
[Rn] 5f² 6d¹ 7s² |
92 |
U |
Uranium |
[Rn] 5f³ 6d¹ 7s² |
93 |
Np |
Neptunium |
[Rn] 5f⁴ 6d¹ 7s² |
94 |
Pu |
Plutonium |
[Rn] 5f⁶ 7s² |
95 |
Am |
Americium |
[Rn] 5f⁷ 7s² |
96 |
Cm |
Curium |
[Rn] 5f⁷ 6d¹ 7s² |
97 |
Bk |
Berkelium |
[Rn] 5f⁹ 7s² |
98 |
Cf |
Californium |
[Rn] 5f¹⁰ 7s² |
99 |
Es |
Einsteinium |
[Rn] 5f¹¹ 7s² |
100 |
Fm |
Fermium |
[Rn] 5f¹² 7s² |
101 |
Md |
Mendelevium |
[Rn] 5f¹³ 7s² |
102 |
No |
Nobelium |
[Rn] 5f¹⁴ 7s² |
103 |
Lr |
Lawrencium |
[Rn] 5f¹⁴ 7s² 7p¹ |
Read about electronic configuration here.
F- block elements, comprising lanthanides and actinides are characterized by the gradual filling of 4f and 5f orbitals. They typically exhibit variable oxidation states, high melting points, and form colored ions. Many typically are also paramagnetic and show complex formation tendencies.
The f block element is made up of two series: Lanthanoid Series and Actinoid Series.
Lanthanide Series are f block elements in which the differentiating electron enters into 4f orbital. Hence this series is also called the 4f series. The common oxidation state of all lanthanides and actinides is +3. Some of the lanthanides also show +2 and +4 oxidation states. Lanthanides form carbides, hydrides, oxides, nitrides, halides etc. The atomic and ionic radii of lanthanides show a gradual decrease with an increase in atomic number. It is known as lanthanoid contraction.
The effect of contraction is a decrease in basicity with an increase in atomic number. As a result of lanthanoid contraction, the atomic radii of the elements which follow lanthanides are similar to those of the elements of the previous period. The pairs of elements Zr-Hf, Nb-Ta, Mo-W and Tc-Re have identical sizes, and similar properties hence these pairs are called chemical twins.
Know more about Isomerism, here.
Actinide Series are f block elements in which the differentiating electron enters into the 5f orbital. Hence this series is also called the 5f series. The common oxidation state of all lanthanides and actinides is +3. In the actinoid series, the elements after uranium are man-made elements hence are called transuranic and synthetic elements. They belong to the 3rd group and the seventh period of the periodic table. The most common oxidation state is +3. Some elements also show +4, +5, +6, +7 oxidation states.
The actinoid elements belong to the second inner transition series in which electrons enter in 5f orbitals (Z = 90 to 103).
Know more about Tautomerism, here.
Read more about Valence Bond Theory, here.
The f block elements of the lanthanide and actinide series involve the filling of orbitals. Lanthanides and actinides have many distinguishing properties.
Feature |
Lanthanides |
Actinides |
Atomic Numbers |
57 to 71 (from Lanthanum to Lutetium) |
89 to 103 (from Actinium to Lawrencium) |
Series Name |
Also known as 4f-block elements |
Also known as 5f-block elements |
Electronic Configuration |
Electrons fill the 4f-orbitals |
Electrons fill the 5f-orbitals |
Occurrence |
Mostly naturally occurring |
Mostly synthetic (except first few elements) |
Radioactivity |
Generally non-radioactive (except promethium) |
Mostly radioactive |
Chemical Reactivity |
Less reactive compared to actinides |
More reactive, especially in moist air |
Oxidation States |
Commonly +3 |
Multiple oxidation states (from +3 to +6) |
Complex Formation |
Forms fewer complexes |
Forms stable and more complex compounds |
Magnetic Properties |
Show paramagnetism |
Show stronger paramagnetism due to unpaired electrons |
Uses |
Used in magnets, catalysts, and alloys |
Used in nuclear reactors and weapons |
Also, learn about inner transition elements here.
There are some similarities between lanthanoids and actinoids, just as there are differences. Here’s a list of the similarities.
Read about d block elements here.
Some examples of how the f block elements can be used are as follows:
Check out other topics of Chemistry, here.
Transition elements are found in groups 3 to 12 of the periodic table. These elements are known for having filled d-orbitals in their valence shell. Here’s an organized list of transition metals by period, with their symbols, atomic numbers, and valence shell configurations.
Group |
Element Name |
Symbol |
Atomic Number |
Valence Shell Configuration |
3 |
Scandium |
Sc |
21 |
3d¹ 4s² |
4 |
Titanium |
Ti |
22 |
3d² 4s² |
5 |
Vanadium |
V |
23 |
3d³ 4s² |
6 |
Chromium |
Cr |
24 |
3d⁵ 4s¹ (exception) |
7 |
Manganese |
Mn |
25 |
3d⁵ 4s² |
8 |
Iron |
Fe |
26 |
3d⁶ 4s² |
9 |
Cobalt |
Co |
27 |
3d⁷ 4s² |
10 |
Nickel |
Ni |
28 |
3d⁸ 4s² |
11 |
Copper |
Cu |
29 |
3d¹⁰ 4s¹ (exception) |
12 |
Zinc |
Zn |
30 |
3d¹⁰ 4s² |
Group |
Element Name |
Symbol |
Atomic Number |
Valence Shell Configuration |
3 |
Yttrium |
Y |
39 |
4d¹ 5s² |
4 |
Zirconium |
Zr |
40 |
4d² 5s² |
5 |
Niobium |
Nb |
41 |
4d⁴ 5s¹ (exception) |
6 |
Molybdenum |
Mo |
42 |
4d⁵ 5s¹ (exception) |
7 |
Technetium |
Tc |
43 |
4d⁵ 5s² |
8 |
Ruthenium |
Ru |
44 |
4d⁷ 5s¹ |
9 |
Rhodium |
Rh |
45 |
4d⁸ 5s¹ |
10 |
Palladium |
Pd |
46 |
4d¹⁰ (no 5s electron) |
11 |
Silver |
Ag |
47 |
4d¹⁰ 5s¹ |
12 |
Cadmium |
Cd |
48 |
4d¹⁰ 5s² |
Group |
Element Name |
Symbol |
Atomic Number |
Valence Shell Configuration |
4 |
Hafnium |
Hf |
72 |
5d² 6s² |
5 |
Tantalum |
Ta |
73 |
5d³ 6s² |
6 |
Tungsten |
W |
74 |
5d⁴ 6s² |
7 |
Rhenium |
Re |
75 |
5d⁵ 6s² |
8 |
Osmium |
Os |
76 |
5d⁶ 6s² |
9 |
Iridium |
Ir |
77 |
5d⁷ 6s² |
10 |
Platinum |
Pt |
78 |
5d⁹ 6s¹ (exception) |
11 |
Gold |
Au |
79 |
5d¹⁰ 6s¹ (exception) |
12 |
Mercury |
Hg |
80 |
5d¹⁰ 6s² |
These include both actinides (f-block) and d-block elements.
Group |
Element Name |
Symbol |
Atomic Number |
Valence Shell Configuration |
— |
Neptunium |
Np |
93 |
5f⁴ 6d¹ 7s² |
4 |
Rutherfordium |
Rf |
104 |
5f¹⁴ 6d² 7s² |
5 |
Dubnium |
Db |
105 |
5f¹⁴ 6d³ 7s² |
6 |
Seaborgium |
Sg |
106 |
5f¹⁴ 6d⁴ 7s² |
7 |
Bohrium |
Bh |
107 |
5f¹⁴ 6d⁵ 7s² |
8 |
Hassium |
Hs |
108 |
5f¹⁴ 6d⁶ 7s² |
9 |
Meitnerium |
Mt |
109 |
5f¹⁴ 6d⁷ 7s² |
10 |
Darmstadtium |
Ds |
110 |
5f¹⁴ 6d⁸ 7s² |
11 |
Roentgenium |
Rg |
111 |
5f¹⁴ 6d⁹ 7s² |
12 |
Copernicium |
Cn |
112 |
5f¹⁴ 6d¹⁰ 7s² |
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