Final answer:
Na (sodium) is the atom that gives up its electrons most easily.
Step-by-step explanation:
The atom that gives up its electrons most easily is Na (sodium).
In the periodic table, sodium (Na) is in group 1A, which is known as the alkali metals. Alkali metals have a single valence electron, which is loosely held and easily lost to form a positive ion. Sodium readily gives up its one valence electron to achieve a stable electron configuration.
Therefore, among the given options, Na is the atom that gives up its electrons most easily.