In Mendeleev’s periodic table, gaps were left for the elements to be discovered later. Which of the following elements found a place in the periodic table later?

In Mendeleev’s periodic table, gaps were left for the elements to be

1.	In Mendeleev’s periodic table, gaps were left for the elements to be discovered later. Which of the following elements found a place in the periodic table later?
A.	Silicon
B.	Germanium
C.	Oxygen
D.	Chlorine
Answer» C. Oxygen