Why do you think Flourine is able to pull the electron away from Lithium?

Because of its high electronegativity.

Explanation:

Fluorine has ability to pull the electron from the lithium because of its high electronegativity.

We know that as we move from left to right in periodic table the number of valance electrons in an atom increase. The atomic size tend to decrease in same period of periodic table because the electrons are added with in the same shell. When the electron are added, at the same time protons are also added in the nucleus. The positive charge is going to increase and this charge is greater in effect than the charge of electrons. This effect lead to the greater nuclear attraction. The electrons are pull towards the nucleus and valance shell get closer to the nucleus. As a result of this greater nuclear attraction atomic radius decreases and electronegativity increases. AS lithium is present on left side of period 2 and fluorine is present on right side of same period. Fluorine is more electronegative while lithium is more electropositive thus fluorine pull the electron from lithium when they combine and form anion while lithium loses its valence electrons and form cation.

oxygen = 21% of the atmosphere

nitrogen = 78%

carbon dioxide = 0.1%

argon =0.934%