Several exceptions apply to the Roman numeral assignment: Aluminum, Zinc, and Silver. Although they belong to the transition metal category, these metals do not have Roman numerals written after their names because these metals only exist in one ion.
Besides, do transition metals form ions?
As you may notice, they can form ions by either losing or gaining electron in 4s orbital. In the chemistry of the transition elements, the 4s orbital behaves as the outermost, highest energy orbital. When these metals form ions, the 4s electrons are always lost first, leading to a positive charge on ion.
What elements form only one cation?
Positive and Negative Ions: Cations and Anions
- The alkali metals (the IA elements) lose a single electron to form a cation with a 1+ charge.
- The alkaline earth metals (IIA elements) lose two electrons to form a 2+ cation.
- Aluminum, a member of the IIIA family, loses three electrons to form a 3+ cation.
- The halogens (VIIA elements) all have seven valence electrons.