Lanthanides: Understanding the Series Count

The question asks for the total number of elements present in the series of lanthanides. This series is a significant part of the periodic table, specifically within the f-block.

What are Lanthanides?

The lanthanide series includes the 15 metallic chemical elements with atomic numbers ranging from 57 to 71. They are named after the element Lanthanum (La), which has atomic number 57. These elements typically start filling the 4f electron shell.

They are often referred to as "rare earth elements," although this term is a bit misleading as many of them are not particularly rare.

Identifying the Lanthanide Elements

The lanthanide series comprises the following elements:

• Lanthanum (La) - Atomic Number 57
• Cerium (Ce) - Atomic Number 58
• Praseodymium (Pr) - Atomic Number 59
• Neodymium (Nd) - Atomic Number 60
• Promethium (Pm) - Atomic Number 61
• Samarium (Sm) - Atomic Number 62
• Europium (Eu) - Atomic Number 63
• Gadolinium (Gd) - Atomic Number 64
• Terbium (Tb) - Atomic Number 65
• Dysprosium (Dy) - Atomic Number 66
• Holmium (Ho) - Atomic Number 67
• Erbium (Er) - Atomic Number 68
• Thulium (Tm) - Atomic Number 69
• Ytterbium (Yb) - Atomic Number 70
• Lutetium (Lu) - Atomic Number 71

Determining the Total Number of Elements

By counting the elements listed above, from Lanthanum (La) to Lutetium (Lu), we find there are exactly 15 elements in the lanthanide series. This count includes Lanthanum (La) and Lutetium (Lu), which complete the 5th and 6th periods and bracket the filling of the 4f orbitals.

Therefore, the series of lanthanides contains 15 elements.