F block elements of the periodic table are found in two series, namely Lanthanoids and Actinoids. Lanthanides are also known as rare earth metals. F block elements are also known as inner transition metals as they provide a transition in the sixth and seventh row of the periodic table.
What Are F Block Elements?
F block elements are those elements of the periodic table whose deep-seated 4f and 5f orbitals are filled with electrons with increasing atomic numbers. F block elements are placed at the bottom of the periodic table. They are a subset of the sixth and seventh periods.
Given below is a list of F block elements
- Lanthanum (La)
- Cerium (Ce)
- Praseodymium (Pr)
- Neodymium (Nd)
- Promethium (Pm)
- Samarium (Sm
- Europium (Eu)
- Gadolinium (Gd)
- Terbium (Tb)
- Dysprosium (Dy)
- Holmium (Ho)
- Erbium (Er)
- Thulium (Tm)
- Ytterbium (Yb)
- Lutetium (Lu)
- Actinium (Ac)
- Thorium (Th)
- Protactinium (Pa)
- Uranium (U)
- Neptunium (Np)
- Plutonium (Pu)
- Americium (Am)
- Curium (Cm)
- Berkelium (Bk)
- Californium (Cf)
- Einsteinium (Es)
- Fermium (Fr)
- Mendelevium (Md)
- Nobelium (No)
- Lawrencium (Lw)
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Types Of F Block Elements
Lanthanoids: The first series of elements in the F block starts with the element Lanthanum, which has the atomic number 51. The elements with atomic numbers 57 to 71 are lanthanoids. Lanthanides are non-radioactive except for promethium which is radioactive.
Actinoids: The second series of elements in the f block start with Actinium which has the atomic number 89. The elements with atomic numbers 89 to 103c are actinoids. Actinides are usually radioactive.
Properties of F Block Elements
- F block elements have electrons added to the f suborbital of the (n - 2) level.
- F block elements are placed between (n - 1)d and ns block elements.
- Many properties of F block elements are similar to D block elements.
Let us look at the properties of lanthanoids and actinoids separately.
Properties Of Lanthanides
- They are soft metals with a light silver colour
- When exposed to air, these metals become dull
- Melting points of these metals ranges from 1000k to 1200k, except for samarium, which has a melting point of 1623k
- These elements are good conductors of heat and electricity
- These elements are non-radioactive in nature except for promethium
- The ionic and atomic radii decrease from lanthanum to lutetium. This is called the lanthanoid contraction.
Properties of Actinides
- These elements have a silvery colour
- These elements usually have a radioactive nature
- These metals are highly reactive and their reactivity increases when finely divided
- The ionic and atomic radii decrease from actinium to lawrencium. This is called actinoid contraction.
- These elements generally have an oxidation state of 3+
Difference Between Lanthanoids and Actinoids
- Lanthanides are involved in the filling of 4f orbitals whereas actinides are involved in the filling of 5f orbitals
- The binding energy of 4f electrons is lesser than the binding energy of 5f electrons
- The shielding effect of 4f electrons is comparatively more effective than 5f electrons
- It is easy to determine the paramagnetic properties of lanthanoids but it is difficult to determine the same for actinides
- Lanthanides are non-radioactive except promethium whereas all actinides are radioactive in nature.
- Lanthanoids do not have a tendency to form oxidations whereas actinides form several oxycations
- Compounds of lanthanides are less basic whereas compounds of actinides are highly basic.
Similarities Between Lanthanoids and Actinoids
- Both lanthanoids and actinoids have an oxidation state of 3+
- Both lanthanoids and actinoids are involved in the filling of (n-2) f orbital
- Both lanthanoids and actinoids are highly electropositive and highly reactive in nature
- With an increase in atomic number, the atomic and ionic sizes of both lanthanoids and actinoids decreases
- Both lanthanoids and actinoids show magnetic properties
This is a brief description of the F block of the modern periodic table. Happy Learning!