Explain the following statement-The magnetic and spectral properties of Lanthanides differ from those of '3d' and '4d' block elements.
Answers
Answer:
Lanthanides are the elements which constitute a distinct series of fourteen elements from
cerium (Ce, Z = 58) to lutetium (Lu, Z = 71). They are so called because these elements succeed
lanthanum (La, Z =57), the element of Group 3 and lie between it and hafnium (Hf, Z = 72),
the element of Group 4, both belonging to third transition series (or 5d-transition series). That
is why they are also known as inner transition elements. These fourteen elements belong to f-
block and are the members of 4f-series because the last or differentiating electron in the atoms
of these elements enters 4f-subshell, i.e., the f-subshell of ante-penultimate shell (here n=6).
Thus, f-block elements have partly filled f-subshells of (n-2)th shell in the elementary or ionic
state.
The first and the last elements of the 4f-series have been mentioned above (i.e., Ce and Lu).
The rest twelve elements along with their symbols and atomic numbers are given below:
praseodymium (Pr, Z = 59), neodymium (Nd, Z = 60), promethium (Pm, Z = 61), samarium
(Sm, Z = 62), europium (Eu, Z = 63), gadolinium (Gd, Z = 64), terbium (Tb, Z = 65),
dysprosium (Dy, Z = 66), holmium (Ho, Z = 67), erbium (Er, Z = 68), thulium (Tm, Z =69)
and ytterbium (Yb, Z = 70). In analogy with various series of d-block elements, these elements
are called first inner transition series elements. All the fourteen elements of the series resemble
closely in their electronic configuration and chemical properties with one another as well as
with lanthanum which may be called a prototype of lanthanide elements. All these elements
said to be the members of Group 3, i.e., Sc group and have been allotted one single position in
the periodic table.