Question

Which element is a bridge element according to Mendeleev?
A.Na
B.Li
C.K
D.Cu

Answer 1

Hint: It is an element of the alkali group of the periodic table. It belongs to the second period and has one electron in the outermost shell. This element shows diagonal relationship with magnesium.

Complete step by step answer:
The bridge element according to Mendeleev in the given options is lithium (Li).
Bridge elements are those elements of the second period which show similar properties with the elements of the third period which are the typical elements.
This relationship of showing similar properties is called the diagonal relationship.
Diagonal relationship is a type of similarity that is found between some of the diagonally adjacent elements of the second period and third period in the periodic table.
Reasons of similarity:
- Similar electronegativity
- Similar ionic or atomic radii
- Similar polarizing power

Diagonal relationship between lithium and magnesium:
a) Similar electronegativity values
b) Both Li and Mg are quite hard and they are lighter than other elements of their group
c) Hydroxides of Li and Mg i.e. \[LiOH\] and \[Mg{{(OH)}_{2}}\] are weak bases.
d) Both form ionic nitrides with the nitrogen in the atmosphere.
\[\begin{align}
  & 6Li+{{N}_{2}}\to 2L{{i}_{3}}N \\
 & 3Mg+{{N}_{2}}\to 2M{{g}_{3}}N \\
\end{align}\]
So, the correct option is B.

Note: Li acts as a bridge element between the elements of group 1 and group 2. It shows similar properties with sodium as both of them are in the same group. It shows almost similar properties with magnesium because of the similar electronegativity values and they cancel out each other due to the polarization of the ions.