What are actinides?
The term ‘actinide series’ has been derived from the first element of the series, actinium. The symbol An is used while referring to any of the actinide series elements which range in the periodic table from atomic numbers 89 to 103.
All actinide series elements are radioactive in nature, they release a large amount of energy on radioactive decay. Uranium and thorium are most abundant naturally occurring actinides on earth, whereas plutonium is synthetically obtained. These elements are used in nuclear reactors and nuclear weapons. Uranium and thorium have diverse current uses, whereas americium is used in ionization chambers of modern smoke detectors. In the modern periodic table lanthanides and actinides are shown as two separate rows below the main periodic table.
General electronic configuration of actinides
The general electronic configuration of actinides is [Rn] 5f1-14 6d0-1 7s2
Here [Rn] is the electronic configuration of the nearest noble gas which is Radium
Lanthanides and Actinides
Lanthanides and actinides belong to the f block of the modern periodic table. They have both similarities and dissimilarities between them; let us compare the properties of lanthanides and actinides.
Similarities between lanthanides and actinides
The elements of lanthanide and actinide series are characterized by filling of (n-2) f subshell. They possess almost similar outermost electronic configuration hence have similar properties. Following are the significant similarities:
- Both have a prominent oxidation state of +3.
- They are involved in the filling of (n-2) f orbitals.
- They are highly electropositive and very reactive in nature.
- With an increase in atomic number, there is a decrease in atomic and ionic size.
- Both show magnetic properties.
Differences between lanthanides and actinides
Lanthanoids are involved in the filling of 4f- orbitals whereas actinoids are involved in the filling of 5f-orbitals. The binding energy of 4f electrons is comparatively less than that of 5f-electrons. The shielding effect of 5f-electrons is less effective as compared to that of 4f-electrons. The paramagnetic properties of lanthanoids can be easily explained but this explanation is difficult in case of actinoids. Lanthanides are non-radioactive in nature except promethium whereas all actinide series elements are radioactive. Lanthanides do not have a tendency to form oxocations, but several oxocations of actinide series exist. The compounds formed by lanthanides are less basic on the other hand the compounds of actinides are highly basic.
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