What can one say for sure about element #99, Einsteinium (Es)) ? a) There's no such element! b) It is an alkali metal. c) It is radioactive. d) It has 253 neutrons. e) It increases one's 1. Q. slightly when swallowed.

Option (C)

Explanation:

Einsteinium is an element of the periodic table grouped in the Actinide series, with atomic number 99. They are dense element and highly electro-positive. They are highly radioactive, i. e the atoms within the element are unstable and constantly decay until they reach a stable environment. It has 99 number of electrons and protons, 153 number of neutrons.

Due to its high radioactivity, they are health hazardous and can used in making nuclear weapons but their uses are very limited and unknown.

Thus, the correct answer is option (C).