Argon has three naturally-occurring isotopes: 99.6% of 40Ar, with an atomic weight of 39.9624 amu, 0.337% of 36Ar, with an atomic weight of 35.9676 amu, and 0.063% of 38Ar, with an atomic weight of 37.9627 amu. Calculate the average atomic weight of Ar. Round off the answer to six significant figures. Do not include the units.

39.9477amu is the average atomic weight of Argon

Explanation:

The average atomic weight is defined as the sum of the products of the atomic weight of each isotope times its abundance. For the Argon the average atomic weight, X is:

X = 39.9477amu is the average atomic weight of Argon

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.

im pretty sure its b