Identify which element is the most metallic - potassium, calcium, scandium, or titanium

Potassium

Explanation:

Potassium is the most metallic among all the choices. The periodic trend of metallic character increases going to the left and down the periodic table. So if you are looking at a periodic table, the elements in the left most column is the most metallic (except for Hydrogen).

Now potassium (K), Calcium (Ca), Scandium (Sc) and Titanium (Ti) are all in period 4 or the 4th row of the periodic table. Potassium is found in the left-most end of the period, so this makes it the most metallic.