Are all elements abbreviated with one or two letters? if not, name some that aren't.

Some elements are abbreviated with more than two letters such as the Ununtrium (Uut), Ununpentium (Uup), Ununseptum (Uus) and Ununoctio (Uuo).

Explanation:

Some elements have intuitive symbology, such as Chlorine (Cl), among others, which are represented by the first letters that make up the name. However, there are others who receive symbols that do not remember the name of the element, such as Lead (Pb). Regardless of the similarity between the names and the symbol of the elements, most of them have the symbol composed of one or two letters, except for the elements Ununtrium (Uut), Ununpentium (Uup), Ununseptum (Uus) and Ununoctio (Uuo).