Why is Lanthanum in the f-block?

Lanthanum:

1. Lanthanum is a chemical element and is represented by the symbol $\mathrm{La}$.
2. It has an atomic number of 57.
3. The electronic configuration of Lanthanum is $\left[\mathrm{Xe}\right]5{\mathrm{d}}^{1}6{\mathrm{s}}^2$.

f-block:

1. Lanthanum is the first element in the lanthanide group of elements which is a rare metal.
2. The $\left[\mathrm{Xe}\right]4{\mathrm{f}}^{1-14}5{\mathrm{d}}^{0-1}6{\mathrm{s}}^2$ electrical configuration of lanthanides is the most common.
3. Lanthanides and actinides are the elements that belong to the f block and they are called inner transition components.
4. Because their additional electron enters (n-2) f orbitals, they are known as f-block elements.
5. These elements have electrons in the f orbital (1 to 14), the preceding energy level's d orbital (0 to 1), and the outermost orbital (0 to 1).

Hence, Lanthanum is in the f-block.