In the case of fluorine, with an atomic number of 9, it indeed has 7 valence electrons in its outermost shell. Fluorine, like other atoms, has a tendency to achieve a stable electron configuration by filling its valence shell. In this process, the nucleus of the atom does play a significant role in attracting electrons, but it is not the only factor involved.
When an atom has fewer than 8 valence electrons, it tends to gain or share electrons to complete its valence shell and achieve a stable configuration, known as the octet rule. Fluorine, with 7 valence electrons, requires only one additional electron to complete its valence shell, which is energetically favorable.
In a chemical reaction or bonding situation, the outermost electrons of one atom can be attracted to the nucleus of another atom. This attraction is due to the electrostatic force of attraction between the positively charged nucleus and the negatively charged electrons. However, it's important to note that atoms themselves do not actively "pull" electrons towards them; rather, electrons are shared, gained, or lost during chemical interactions based on the electron configuration and the energetically favorable state.
In the case of fluorine, it tends to attract an additional electron from another atom to complete its valence shell and achieve a stable electron configuration. This is commonly observed in ionic bonding, where fluorine can gain an electron to form the fluoride ion (F-) or in covalent bonding, where it can share electrons with another atom to complete its valence shell.
In summary, while the nucleus plays a crucial role in attracting electrons, the tendency of atoms to gain or share electrons to achieve a stable electron configuration is determined by various factors, including the valence electron count and the octet rule.