The element that gives up its valence electrons most readily among the options provided is Fr (Francium).
Francium is an alkali metal located in Group 1 of the periodic table, which means it has only one valence electron. Alkali metals are known for their high reactivity and willingness to lose their single valence electron to form positive ions. In contrast, elements like Bi (Bismuth) and Be (Beryllium) have more valence electrons and do not lose them as readily, and Ar (Argon) is a noble gas with a complete valence shell, making it very stable and unreactive.
So, the correct answer is Fr (Francium).