Transition metals form ions with different charges. An iron(II) ion has a 2+ charge, and an iron(III) ion has a 3+ charge.

Can France claim the first periodic ... table contained just 28 elements, organised by their valency (how many other atoms they can combine with). These elements were almost entirely main group ...

The periodic table - AQA Mendeleev made an early periodic ... so they are similar in their chemical properties. Transition metals - AQA The transition elements are metals. They have high melting ...