Part B Mendeleev placed thallium (Tl) in the same group as lithium (Li), sodium (Na), potassium (K),
rubidium (Rb), and cesium (Cs). However, the modern periodic table doesn't place thallium in
this group. Use the periodic table C to find the properties of thallium. Explain why
Mendeleev might have grouped thallium in the same group as lithium and sodium. Also
eynlain how thallium is different from the other five elements

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. 

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