In period 3 of the periodic table, there are no transition metals. Period 3 consists of the elements sodium (Na), magnesium (Mg), aluminum (Al), silicon (Si), phosphorus (P), sulfur (S), chlorine (Cl), and argon (Ar). All these elements are classified as main group elements rather than transition metals.
Transition metals are defined as elements that have an incomplete d subshell or can give rise to cations with an incomplete d subshell. The transition metals are found in the d-block of the periodic table, which begins in period 4. Therefore, since period 3 does not include any d-block elements, it does not contain any transition metals.