Question

A noble gas consists of three isotopes of masses of 19.99 amu, 20.99 amu, and 21.99 amu. the relative abundances of these isotopes are 90.92%, 0.257%, and 8.82% respectively. what is the average atomic mass of this noble gas? what noble gas is this?

Answer 1

Answer:

               Neon

Explanation:

Average Atomic Mass is calculated using following formula,

= [ (Mass of Isotope 1 × % Natural Abundance) + (Mass of Isotope 2 × % Natural Abundance) + ...... (Mass of Isotope n × % Natural Abundance) ] ÷ 100

Data Given:

                    Mass of Isotope 1  =  19.99 amu

                    % Natural Abundance of Isotope 1  =  90.92

                    Mass of Isotope 2  =  20.99 amu

                    % Natural Abundance of Isotope 2  =  0.257

                    Mass of Isotope 3  =  21.99 amu

                    % Natural Abundance of Isotope 3  =  8.82

Solution:

Putting values in formula,

Average Atomic Mass  = [ (19.99 × 90.92) + (20.99 × 0.257) + (21.99 × 8.82) ] ÷ 100

Average Atomic Mass  =  (1817.49 + 5.394 + 193.95) ÷ 100

Average Atomic Mass  =  20.16

Result:

            Consulting Periodic Table it was found that the noble gas with Average Atomic Mass of 20.16 ≈ 20.18 is Neon.