The definition of f block elements refers to a group of elements in the periodic table that belong to the inner transition metals. They are characterized by their filling of the f-orbitals in their electron configurations. This block includes two series of elements: the lanthanides, 58 (Cerium) to 71 (Lutetium) and the actinides, 90 (Thorium) to 103 (Lawrencium). f-block elements in the periodic table placed separately at the bottom.
They are unique for their position in the periodic table, having electron configurations that fill f-orbitals, resulting in similar chemical properties within each series.
These elements have specific electronic configurations and exhibit a range of oxidation states, leading to diverse chemical properties used in various applications.
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f-block Elements
The f-block elements, commonly known as the inner transition metals. They consist of two series: the lanthanides and the actinides. These elements exhibit similarities in their electronic configurations and chemical properties due to the filling of f-orbitals. If we talk about the position of f block elements in the Periodic table, f block elements in the Periodic table are placed separately at the bottom.
The lanthanide series comprises the 14 elements following lanthanum, ranging from cerium to lutetium. Actinides are the 14 elements succeeding actinium, starting with thorium and extending to lawrencium.
The f-block elements, also known as inner transition metals, are found in the two series located at the bottom of the periodic table. These elements belong to the lanthanide and actinide series, distinguished by their placement within the f-orbital block.
Related Video:
2.0Classification of f block elements
As we discussed above, f-block elements are classified into two series: the lanthanides and the actinides. The lanthanides belong to the sixth period and are located between groups 3 and 4, while the actinides belong to the seventh period and follow the lanthanides. These series consist of elements with partially filled f-orbitals.
Firstly let’s discuss the general differences between Lanthanides and Actinides in brief-
Lanthanides
Actinides
These elements range from atomic number 58 (Cerium) to 71 (lutetium).
These elements range from atomic number 90 (Thorium) to 103 (Lawrencium).
They are typically shiny metals, often silvery-white in appearance.
Most actinides are synthetic and highly radioactive.
Lanthanides share common properties due to similar electron configurations within the f-orbital.
Uranium and plutonium are the most well-known actinides due to their nuclear applications.
Electronic Configuration of Lanthanides and Actinides:
The electronic configurations of the lanthanides and actinides are defined by the filling of their f-orbitals.
For the lanthanide series (also known as the rare earth elements), the general outer electronic configuration can be expressed as [Xe] 4f(1-14) 5d0 6s2. Each successive element adds one electron to the 4f sublevel, maintaining the 6s2 and 5d0 configuration.
Atomic Number
Element
Symbol
Outer electronic configuration
58
59
60
61
62
63
64
65
66
67
68
69
70
71
Cerium
Praseodymium
Neodymium
Promethium
Samarium
Europium
Gadolinium
Terbium
Dysprosium
Holmium
Erbium
Thulium
Ytterbium
Lutetium
Ce
Pr
Nd
Pm
Sm
Eu
Gd
Tb
Dy
Ho
Er
Tm
Yb
Lu
4f1 5d16s2
4f3 6s2
4f4 6s2
4f5 6s2
4f6 6s2
4f7 6s2
4f7 5d1 6s2
4f9 6s2
4f10 6s2
4f11 6s2
4f12 6s2
4f13 6s2
4f14 6s2
4f14 5d1 6s2
Actinides follow a similar pattern, with the outer electronic configuration commonly expressed as [Rn] 5f(1-14) 7s2. As with the lanthanides, each successive element adds electrons to the 5f sublevel while retaining the 7s2 configuration.
Atomic No.
Elements
Symbol
Electronic Configuration
90
91
92
93
94
95
96
97
98
99
100
101
102
103
Thorium
Protactinium
Uranium
Neptunium
Plutonium
Americium
Curium
Berkelium
Californium
Einsteinium
Fermium
Mendelevium
Nobelium
Lawrencium
Th
Pa
U
Np
Pu
Am
Cm
Bk
Cf
Es
Fm
Md
No
Lr
5f06d27s2
5f26d17s2
5f36d17s2
5f46d17s2
5f66d07s2
5f76d07s2
5f76d17s2
5f96d07s2
5f106d07s2
5f116d07s2
5f126d07s2
5f136d07s2
5f146d07s2
5f146d17s2
3.0Properties of f block elements
The f-block elements, comprising the lanthanoids and actinoids, exhibit a range of unique properties that distinguish them from other elements in the periodic table.
In this section, we will discuss general properties of lanthanides and actinides.
Properties of Lanthanides
Lanthanides, also known as rare earth elements, exhibit several notable physical properties:
1. Metallic Nature: Lanthanides are silvery-white, malleable metals with high electrical conductivity.
2. High Density: They possess high densities; however, their densities vary across the series.
3. High Melting and Boiling Points: Lanthanides generally have high melting and boiling points, with some exceptions among the lighter lanthanides.
4. Magnetic Properties: Several lanthanides display unique magnetic properties, such as paramagnetism or ferromagnetism, especially at low temperatures.
5. Reduced Reactivity: Lanthanides are relatively reactive but tarnish slowly in air due to the formation of an oxide layer on their surface.
6. Variable Oxidation States: Lanthanides can exhibit different oxidation states, although the +3 oxidation state is the most common in compounds.
Lanthanides
Oxidation State
Ce58
Pr59
Nd60
Pm61
Sm62
Eu63
Gd64
Tb65
Dy66
Ho67
Er68
Tm69
Yb70
Lu71
+3, +4
+3, (+4)
+3
+3
(+2), +3
+2, +3
+3
+3, +4
+3, (+4)
+3
(+2), +3
(+2), +3
+2, +3
+3
7. Similarity in Properties: The lanthanides share many chemical and physical characteristics due to their similar electronic configurations.
Properties of Actinides:
1. Radioactivity: Most actinides are radioactive, exhibiting different types of radioactive decay like alpha, beta, and gamma decay.
2. High Density: Actinides have high densities; for instance, uranium and plutonium are notably dense metals.
3. High Melting and Boiling Points: Actinides generally have high melting and boiling points, attributed to strong metallic bonding within their structures.
4. Variable Valency: These elements often exhibit various oxidation states due to the partially filled 5f orbitals, resulting in different valencies and chemical reactivities. The highest oxidation state is +7 (unstable) for Np and Pu, while the highest stable oxidation state is +6 for U.
Actinides
Oxidation state
Th90
Pa91
U92
Np93
Pu94
Am95
Cm96
Bk97
Cf98
Es99
Fm100
Md101
No102
Lr103
+4
(+4), +5
(+3), (+4), (+5), +6
(+3), (+4), +5, (+6), (+7)
(+3), +4, (+5), (+6), (+7)
+2,(+3),(+4),(+5),(+6)
+3, (+4)
+3, (+4)
+3
+3
+3
+3
+3
+3
5. Magnetic Properties: Some actinides display unique magnetic properties at low temperatures due to the interaction of their electronic orbitals.
6. Allotropy: Some actinides exist in multiple structural forms (allotropes) under different conditions, altering their physical properties.
4.0Similarities between Lanthanides and Actinides :
Both lanthanides and actinides share several similarities:
Inner Transition Metals:
Both series are categorized as inner transition metals, occupying the f-block of the periodic table.
Similar Electronic Configurations:
They have similar electronic configurations, with the electrons filling their f-orbitals. Lanthanides fill the 4f orbitals, while actinides fill the 5f orbitals.
Chemical Properties:
Both series exhibit similar chemical properties within their respective groups due to the filling of inner electron shells, resulting in comparable chemical behavior.
Radioactive Elements:
Many actinides are radioactive, and some of the heavier lanthanides exhibit slight radioactivity as well.
Applications:
Both lanthanides and actinides find applications in various industries, albeit for different reasons. Lanthanides are used in technologies like lighting, catalysts, magnets, and electronics, while actinides are employed in nuclear reactors, research, and sometimes in nuclear weaponry.
5.0Differences between Lanthanides and Actinides:
Lanthanides and actinides are two series of elements classified as inner transition metals, but they have several differences:
Here's a summary table to highlight the differences between lanthanides and actinides:
Aspect
Lanthanides
Actinides
Electronic Configuration
4f sublevel partially filled
5f sublevel partially filled
Occurrence
More abundant, naturally found in Earth's crust
Predominantly synthetic, found in trace amounts due to radioactivity
Stability
Generally more stable, longer half-lives
Often radioactive, less stable
Applications
Electronics, catalysts, magnets, lighting
Nuclear reactors, research, nuclear weaponry
Position in Periodic Table
Sixth period
Seventh period
Properties
Relatively uniform properties and chemical behaviors
Greater variability in properties and behaviors
Table of Contents
1.0What are f-block elements
2.0Classification of f block elements
3.0Properties of f block elements
3.1Properties of Lanthanides
3.2Properties of Actinides:
4.0Similarities between Lanthanides and Actinides :
