Question

How many elements make up the lanthanide series?

Answer 1

The f-block consists of two series lanthanoids and actinoids. Lanthanoids resemble one another more closely than do the members of ordinary transition elements in any series. They have only one stable oxidation state and their chemistry provides an opportunity to examine the effect of small size and nuclear charge along a series of otherwise similar elements.

Complete step-by-step answer: It may be noted that the atoms of Lanthanoids have electronic configuration as $6{{s}^{2}}5{{d}^{0\,or\,1}}4{{f}^{1-14}}$.
The Lanthanide series consists of fifteen elements ranging from Atomic number $57-71$. The elements of the lanthanide series are depicted below:

Atomic number	Name of the Lanthanoid element	Symbol of the Lanthanide element
$57$	Lanthanum	La
$58$	Cerium	Ce
$59$	Praseodymium	Pr
$60$	Neodymium	Nd
$61$	Promethium	Pm
$62$	Samarium	Sm
$63$	Europium	Eu
$64$	Gadolinium	Gd
$65$	Terbium	Tb
$66$	Dysprosium	Dy
$67$	Holmium	Ho
$68$	Erbium	Er
$69$	Thulium	Tm
$70$	Ytterbium	Yb
$71$	Lutetium	Lu

Elements of the lanthanide series have many properties. Some of these are mentioned below.
1. They all are highly reactive metals.
2. These are good conductors of electricity.
3. All the elements of lanthanide series are silvery white soft metals and tarnish rapidly.
4. Density and other properties changes smoothly except for Eu and Yb and occasionally for Tm.

Note: Elements of Lanthanide series have many useful applications. They are used in the production of alloy steels for plates and pipes. They are also used in preparation of Misch metal, they also find their applications in petroleum cracking. Some oxides are used in television screens and similar fluorescing surfaces.