Now, lithium has three electrons and three protons. So its nucleus is composed of only three protons, while its inner shell is composed of two electrons, and its outer shell is composed only of a single electron. Now let's look at the fluorine. Fluorine has nine protons in its nucleus. While two electrons are found in the inner shell, seven electrons are found on the outer shell. And that means because we have a higher nuclear or effective nuclear charge, we have a higher force.