Letter c. their valence electron is only one since they belong to group I in the periodic table. their atomic masses arent even close to each other. hydrogen weighs only 1 amu (average weight) while potassium is 38 amu. Mass of neutrons, they dont have equal number of neutrons, *as far as i know* in fact they are far from each other. Hydrogen has the atomic number 1 while K is 19. and so their energy levels. H has 1s while K is 1s two 2s two 2p six 3s two 3p six 4s one
C.number of valence electrons
1 5 1