Why are some elements on the periodic table separated?

Answer 1

Simply for convenience. Were it included in the rest of the table those elements would fit between the transition ans alkaline-earth metals, and make the table too wide to be easily displayed on most pages.:-))))

Answer 2

Lanthanide Series and Actinide Series

There are a couple reasons why the Lanthanide and Actinide Series are separated on the Periodic Table. One, they are put on the bottom of the periodic table mainly for aesthetic purposes (so the periodic table display isn't so wide).

Two, it also has to do with the electron configurations(how electrons are distributed among the orbitals of an atom) of the elements in both of these series.

In brief terms:

All of the elements in the Lanthanid series fill the 4f electron sublevel before the second 5d electron sublevel ever gets filled.

With the Actinide series elements, the 5f electron sublevel is filled before the 6d electron sublevel gets filled.

Hydrogen

Hydrogen is considered to be a unique element, as it only has 1 electron thus exhibiting some unique behavior. It can either gain an electron (alkali metal-like behavior) and gain an electron configuration identical to that of Helium or lose an electron and be just a lone proton (halogen-like behavior). It is often categorized as an alkali metal due to it having only 1 electron in its outermost shell (in this case, its only electron shell), although hydrogen is not actually a metal. It is being debated by some as to whether hydrogen should be classified as an alkali metal or as a halogen.

Answer 3

Elements on the periodic table are separated based on their properties and characteristics. They are grouped together according to shared traits, such as similar chemical behaviors. This organization helps scientists understand relationships between elements and predict their properties.

Answer 4

Rare earth metals are an extremely reactive group on the periodic table. They are rare because they tend to react with everything, so are usually not found pure.

Answer 5

because when it was made those metals were not discovered yet and they all fit in between two different elements