2. Rank each of the following in order of DECREASING atomic radius
Ca, Rb, C.

Rb > Ca > C

Explanation:

The order of decreasing atomic radius of the elements given is Rb > Ca > C.

Atomic radius of a substance is the half of the internuclear distance between two covalently bonded atoms of non-metallic elements or half of the distance between two nuclei in the solid state of metals.

Therefore, Rubidium from the choices has the greatest atomic radius and Carbon has the lowest.

c is having 4 valence electrons and is bonded to three hydrogens and one sulphur atom, therefore, the number of bond pair is equal to four. as all the valence electrons are used in forming the bonds so, there is no lone pair left on carbon.

s is having 6 valence electrons and is bonded to one other sulfur atom and one carbon atom, therefore, the number of bond pair is equal to 2. as only two valence electrons are used in forming the bonds so, four electrons are left. therefore, two lone pairs are present on s.