Question

Identify the elements that weren't arranged in theincreasing order of atomic mass in the Mendeleev's periodic table.
1..Potassium and Calcium
2.. Cobalt and Iron
3..Tellurium and lodine
4..Titanium and Vanadium​

Answer 1

Answer:

Gallium, germanium, and scandium were all unknown in 1871, but Mendeleev left spaces for each and predicted their atomic masses and other chemical properties. Within 15 years, the “missing” elements were discovered, conforming to the basic characteristics Mendeleev had recorded.