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.

(a) noble gases: Helium

(b) alkaline earth metals: Beryllium

(c) alkali metals: Lithium

(d) chalcogens: Oxygen

Explanation:

The periodic table is characterized in that some of its groups are recognized by their names that are based on the properties and characteristics of their group. An example of this are the compounds of group I (alkali metals, except for hydrogen), those of group 2 are called alkaline earth metals, and so on.