Question

The elements in the middle of the periodic table are called:
A.Metalloids
B.Transition elements
C.Rare earth elements
D.Noble gases

Answer 1

Hint: Noble gas: The elements of the group $18$, are known as noble gas. For example: helium, neon.Rare earth elements: There are a total seventeen rare earth elements known. All actinides and all lanthanides along with scandium and yttrium are rare earth elements.

Complete step by step answer:
Transition elements: Those elements which are in groups from three to eleven. They are called a transition because they are in between the s- block elements and p-block elements. For example: Scandium, iron, zinc, etc. They have fully or at least one electron in their d-orbits. For example: scandium has one d-electron, zinc has ten d-electrons. Due to the different number of electrons present in their d-shells they show different valencies. For example: Scandium having one electron can show three valencies as one, two and three. Because the atomic number of scandium is $21$and its electronic configuration is $Ar3{d^1}4{s^2}$. By losing only one s-electron it will attain one valency and by losing both the s-electrons it will attain valency two. And by losing two s-electrons and one d-electron it will achieve three valencies which is a stable state of scandium. Because after losing three electrons it will attain electronic configuration of noble gas argon.
Noble gas: The elements of the group $18$, are known as noble gas. For example: helium, neon, argon, krypton, etc. They are placed at the right side of the periodic table.
Rare earth elements: Lanthanides, actinides (the two separate rows in the periodic table) and scandium, yttrium and lanthanum, are known as rare earth elements. There are a total $17$ rare earth elements known.
Metalloids are those elements which show the properties of metals as well as the properties of nonmetals, are known as metalloids.
Transition elements are placed in the middle of the periodic table.

Hence option B is correct.

Note:
Generally noble gases do not react with other elements at room temperature. So they are also known as inert gases. They have completely filled orbitals i.e. two, eight or eighteen according to their atomic numbers. So they are very less reactive. And highly stable.