The number of elements from the following that do not belong to lanthanoids is:

and

Question

The number of elements from the following that do not belong to lanthanoids is:

and

Canvas Classes · Accepted Answer

Lanthanoids: Elements with Z = 57 (La) to 71 (Lu) — filling 4f orbitals.

Checking each element:

| Element | Z | Lanthanoid? |
|---------|---|-------------|
| Eu (Europium) | 63 | Yes ✓ |
| Cm (Curium) | 96 | No ✗ (Actinoid) |
| Er (Erbium) | 68 | Yes ✓ |
| Tb (Terbium) | 65 | Yes ✓ |
| Yb (Ytterbium) | 70 | Yes ✓ |
| Lu (Lutetium) | 71 | Yes ✓ |

Only Cm (Z=96) is NOT a lanthanoid — it is an actinoid (5f series).

Count = 1

Answer: Option (3) — 1

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