Chemistry - The f-block
The periodic table can be regarded as having four distinct blocks - s, p,
d, and f - with elements located there according to the outermost subshell
being filled. We have dealt with the s and p blocks - the main group
elements, and the d block - the transition elements. But what about the
Study of the periodic table shows that the f-block elements interrupt the
third and fourth series of the transition metals.
The f-block contains two sets of elements:
* the lanthanides, which follow the element lanthanum - La
* the actinides, which follow the element actinium - Ac.
The lanthanides are a 14-element set following the element lanthanum, with
all elements characterised by having the as their outermost
The actinides are a 14-element set following the element actinium, with
all elements characterised by having the as their outermost (highest
Notable among the lanthanides and actinides are uranium (element number 92
- involved in fission reactions) and the transuranium elements  -
produced from uranium.
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