Rubidium has two common isotopes ^85rb and ^87 rb if the abundance of ^85rb is 72.2% and the abundance of ^87 rb is 27.8% what is the average atomic mass of rubidium

he would use the colour black

the answer is d. 74.02

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.