which element has the smallest atomic radius?\ncalcium\npotassium\nscandium\ntitanium

Explanation:

Step1: Recall periodic - trend of atomic radius

Atomic radius decreases across a period (from left to right) in the periodic table. This is because as the atomic number increases across a period, the number of protons in the nucleus increases, leading to a greater nuclear charge. The electrons are added to the same energy level, and the increased nuclear charge pulls the electrons closer to the nucleus, reducing the atomic radius.

Step2: Locate the elements in the periodic table

Calcium (Ca) has atomic number 20, potassium (K) has atomic number 19, scandium (Sc) has atomic number 21, and titanium (Ti) has atomic number 22. These elements are all in the fourth period of the periodic table.

Step3: Determine the element with the smallest radius

Since they are in the same period, the element with the highest atomic number among them will have the smallest atomic radius. Among potassium (K), calcium (Ca), scandium (Sc), and titanium (Ti), titanium has the highest atomic number (22).

Answer:

titanium