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?

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.