Short answers, pulled from the story.
Dmitri Mendeleev published the first periodic table that gained general acceptance in 1869. He arranged elements by increasing atomic mass and noticed a recurring pattern in their chemical properties.
Germanium appeared in 1886 with properties aligning closely to his calculations. Mendeleev described this unknown substance as having a low melting point and high density before it was found.
Tennessine was synthesized in 2009 while oganesson had been created earlier in 2002. These last two elements received official names in 2016.
By 2010, all 118 known elements existed, completing the first seven rows of the table. Tennessine was synthesized in 2009, while oganesson had been created earlier in 2002.
Relativistic effects alter properties for heavy elements beyond atomic number 104. Gold appears golden and mercury remains liquid due to these forces caused by highly charged nuclei.