JEE Main 2024 — D And F Block Elements Question with Solution

To determine the number of elements from the given list that do not belong to the lanthanoids, let's first define what lanthanoids are. The lanthanoids consist of the 15 chemical elements in the periodic table from Lanthanum ($\mathrm{La}$) with atomic number 57 to Lutetium ($\mathrm{Lu}$) with atomic number 71. Thus, lanthanoids include:

• Lanthanum ($\mathrm{La}$)
• Cerium ($\mathrm{Ce}$)
• Praseodymium ($\mathrm{Pr}$)
• Neodymium ($\mathrm{Nd}$)
• Promethium ($\mathrm{Pm}$)
• Samarium ($\mathrm{Sm}$)
• Europium ($\mathrm{Eu}$)
• Gadolinium ($\mathrm{Gd}$)
• Terbium ($\mathrm{Tb}$)
• Dysprosium ($\mathrm{Dy}$)
• Holmium ($\mathrm{Ho}$)
• Erbium ($\mathrm{Er}$)
• Thulium ($\mathrm{Tm}$)
• Ytterbium ($\mathrm{Yb}$)
• Lutetium ($\mathrm{Lu}$)

Given the list of elements: Eu (Europium), Cm (Curium), Er (Erbium), Tb (Terbium), Yb (Ytterbium), and Lu (Lutetium), we can now check which of these are not part of the lanthanoids:

• $\mathrm{Eu}$ (Europium) belongs to the lanthanoids.
• $\mathrm{Cm}$ (Curium) does not belong to the lanthanoids; it is an actinoid.
• $\mathrm{Er}$ (Erbium) belongs to the lanthanoids.
• $\mathrm{Tb}$ (Terbium) belongs to the lanthanoids.
• $\mathrm{Yb}$ (Ytterbium) belongs to the lanthanoids.
• $\mathrm{Lu}$ (Lutetium) belongs to the lanthanoids.

From the given list, only Cm (Curium) does not belong to the lanthanoids, which means the correct answer is:

Option B: 1