The type of oxide formed by the element among Li, Na, Be, Mg, B and Al that has the least atomic radius is :

The elements given are Li, Na, Be, Mg, B, and Al. We need to find which has the least atomic radius.

Atomic radii (approximate, in pm):

Li: 152, Na: 186, Be: 112, Mg: 160, B: 87, Al: 143

Boron (B) has the smallest atomic radius among these elements (approximately 87 pm).

Boron has atomic number 5 with electronic configuration $$1s^2 2s^2 2p^1$$. It is a metalloid in Group 13.

The oxide of boron is $$B_2O_3$$ (boron trioxide), which has the formula $$A_2O_3$$ where A = B.

$$B_2O_3$$ is an acidic oxide.

The answer is Option B: $$A_2O_3$$.