When a lithium atom becomes ionized its new electron configuration is 4 points the same as which element?

A. Ar
B. Mg
C. He
D. Fe

C. He

Explanation:

When lithium is ionized, its new electronic configuration is the same as that of a helium atom.

 Lithium is made up of 3 electrons with a configuration of:

                     2, 1

it has 1 electron in its outermost shell.

As a metal lithium will prefer to lose an electron due to its electropositivity.

    On losing an electron, it will have 2 electrons remaining

Now, Helium has 2 electrons and this makes it similar to Lithium that has lost one electron.

This makes Lithium isoelectronic with Helium.