Using the periodic table, identify the lightest member of each of the following groups:
(a) noble gases
(b) alkaline earth metals
(c) alkali metals
(d) chalcogens

(a) noble gases He ( helium)

(b) alkaline earth metals Be (berilium)

(c) alkali metals Li (litium)

(d) chalcogens O (oxygen)

Explanation:

The lightest element is the one who has the lowest molecular mass.

in all groups as noble gases, alkaline earth metals, alkali metals, chalcogens, the lightest element s the first of the group, that's because the molecular weight increase when the atomic number increase.

h let me think