Asked by ravikumar1998,
48 weeks ago
Elements 58-71 contain lanthanoids, and elements 90-103 include actinoids. Lanthanoids, due to poor 4f-orbital shielding, cause the atomic radii of elements after them to be much lower than expected. This is termed contractions in lanthanide. Actinoids are all radioactive and most are not found naturally on earth.
127 weeks ago
Lanthanoids include 14 elements, with atomic numbers 58-71:
The actinoid series also includes 14 elements, with the atomic numbers 90-103: