The major difference between a 1s orbital and a 2s orbital is that The 2s orbital has a slightly different shape.
The 2s orbital is at a higher energy level.
The 2s orbital can hold more electrons.
The 1s orbital can have only one electron.

The 2s orbital is at a higher energy level.

Explanation:

1s and 2s are present in the s sub-orbital which surrounds the nucleus. The s sub-orbital has a spherical shape. As per the level of the energy, the sub-orbitals are numbered as 1s, 2s, 3s, 4s, etc. respectively. The difference among the sub-orbitals is based on their level of energy. 1s has less energy level than 2s. The radius of 2s is more than 1s.

the answer for sodium is 0.186

the answer for rubidium is 0.251