A quantum dot includes: a core including at least one first positive ion precursor and at least one negative ion precursor; a shell including at least one second positive ion precursor and at least one negative ion precursor and wrapping the core; and a ligand formed on a surface of the shell, wherein the first positive ion precursor is an n-period element and the second positive ion precursor is an (n-1)-period element, where n is an integer of 3 to 6.