Question

what is the relation between number of orbits and atomic size ?​

Answer 1

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Size of Orbitals and Atomic Radii. The size of the orbital determines the radius of an atom. As you go down a group on the periodic table, the size of the orbital increases meaning the atomic radius increases as well. The increase of size in the orbital is due to the increase of the quantum number "n"

Answer 2

if the number of orbits is same across a period then the atomic size decreases from left to right across a period