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