Which atom has the lowest ionization energy in period 3?

In Period 3 of the Periodic Table, sodium (Na) has the lowest ionization energy. This is because ionization energy generally increases across a period due to increasing nuclear charge, which holds the electrons more tightly. Sodium, being the first element in Period 3, has a relatively low nuclear charge compared to the other elements in the same period, making it easier to remove its outermost electron.