Statement I: Lithium needs less energy to knock off an electron from its outermost orbit than Helium.
Statement II: Lithium has 1 electron in its outermost orbit which is loosely bound due to the repulsion of the inner orbit electrons and hence, less attraction from the nucleus.
Statement I is true. Statement II is true. Statement II is the correct explanation of statement I.
In Lithium, 2 electrons are in the first orbit and the remaining electron is in the second orbit. This electron experiences less attraction from the nucleus due to the increased distance of the orbit. Also, the electrons in the first orbit repel the 3rd electron which further reduces the net effective force on the outermost electron.
Hence, it is easy to knock off the outermost electron in Lithium when compared to Helium.