The atomic weight of tellurium ($Te$) is $128$ and store of iodine ($I$) is $127$. Even though iodine has a lower atomic weight, Mendeleev placed tellurium before iodine in his periodic table.

Explain why Mendeleev reversed the order of these two elements.

Mendeleev left empty spaces in his periodic table.

Explain why leaving these spaces made his table more widely accepted after several years.

Tennessine ($Ts$) is located at the absolute bottom of Group 7, directly below astatine ($At$) in the modern periodic table.

Predict:

1. The chemical formula of a tennessine molecule.
2. The state of matter of tennessine at room temperature ($20^{\circ }C$).