Mendeleev's predicted elements

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Dmitri Mendeleev published a periodic table of the chemical elements in 1869 based on properties that appeared with some regularity as he laid out the elements from lightest to heaviest.^[1] When Mendeleev proposed his periodic table, he noted gaps in the table and predicted that then-unknown elements existed with properties appropriate to fill those gaps. He named them eka-boron, eka-aluminium, eka-silicon, and eka-manganese, with respective atomic masses of 44, 68, 72, and 100.