In 1869, Dmitri Mendeleev published his periodic table, arranging the elements known at the time.
Tellurium (Te\text{Te}Te) has a relative atomic mass of 127.6, and iodine (I\text{I}I) has a relative atomic mass of 126.9. Explain why Mendeleev placed tellurium before iodine in his periodic table.
Mendeleev left several gaps in his table for undiscovered elements, such as the gap below silicon which he named 'eka-silicon'. Explain how Mendeleev's predictions regarding these gaps led to the widespread acceptance of his periodic table.
In the modern periodic table, elements are arranged in a different order compared to Mendeleev's table. State the property used to arrange elements in the modern periodic table.