The f-block consists of the lanthanoids and actinoids. Lanthanum, closely resembling lanthanoids, is typically included in discussions of the lanthanoids, often denoted by the general symbol Ln.
What does the f-block comprise, and how is lanthanum usually treated in discussions of the lanthanoids?
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The f-block comprises the lanthanides and actinides, both series of inner transition metals. The lanthanides, also known as lanthanoids, include elements with atomic numbers 57 to 71, starting with lanthanum (La). In discussions of the lanthanoids, lanthanum is often treated separately due to its lack of f-electron involvement. Lanthanum is usually considered a part of the d-block and is not categorized with the other lanthanides in terms of f-orbital characteristics. This differentiation arises because lanthanum has a 5d¹ configuration instead of the characteristic f-orbital configuration seen in the rest of the lanthanides.