Which of the following elements has the largest atomic radius out of these elements? Lithium Boron Fluorine Potassium Rubidium

Rb > K > Li > B > F

Explanation:

Atomic radius  trend along period:

As we move from left to right across the periodic table the number of valance electrons in an atom increase. The atomic size tend to decrease in same period of periodic table because the electrons are added with in the same shell. When the electron are added, at the same time protons are also added in the nucleus. The positive charge is going to increase and this charge is greater in effect than the charge of electrons. This effect lead to the greater nuclear attraction. The electrons are pull towards the nucleus and valance shell get closer to the nucleus. As a result of this greater nuclear attraction atomic radius decreases.

That's why fluorine has smaller atomic radius from given elements because it is present on right hand side and experience greater nuclear attraction.

Atomic radii trend along group:

As we move down the group atomic radii increased with increase of atomic number. The addition of electron in next level cause the atomic radii to increased. The hold of nucleus on valance shell become weaker because of shielding of electrons thus size of atom increased.

So from given elements Rubidium has greater atomic radius because of large atomic number and thus experience smaller nuclear attraction.

Rb > K > Li > B > F