SIMPLE ANSWERS ONLY I ALREADY GOOGLED AND DIDN'T FIND ANYTHING PLEASE ANSWER IN YOUR OWN WORDS. How is atomic mass calculated for elements on the periodic table.

Explanation:

The atomic mass of elements on the periodic table are derived from the proportion of the geonormal abundance of the different isotopes of an element.

Using a mass spectrometer, the proportion/percentage/fraction by which each of the isotopes of an element occurs in nature is determined. This proportion is the geonormal abundance. From this the atomic mass of the element can be derived. Simply multiply the mass by the abundance and sum the values for the same isotopes together.

Mass is the amount of matter in an object.  weight is the measurement of the pull of gravity on an object.  say for example, you travel to the moon which has a different gravitational field compared to the gravitational field of earth. (gravitational fields: earth = 1, moon = 0.165)  now when you are on the moon, the pull of gravity on you is different than on the earth. and as weight is the measurement of the pull of gravity on an object, that means yes, your weight can and will change on the moon.  however, on the moon, on earth or even on jupiter, the amount of mass inside of you remains the same. meaning your physical mass remains constant.  in conclusion it is possible for your weight to change as your mass remains constant.