An isoelectronic species has the same number of electrons. Fluorine (F) has 9 electrons. Therefore, any ion or atom with 9 electrons is isoelectronic with fluorine.

Here are a few examples:

* O^2- (oxide ion): Oxygen has 8 electrons, and the 2- charge adds 2 more, giving a total of 9.

* N^3- (nitride ion): Nitrogen has 7 electrons, and the 3- charge adds 3 more, giving a total of 9.

* Ne (neon): Neon is a noble gas with 10 electrons, but it has lost one electron to become a +1 cation, leaving 9 electrons.

Let me know if you would like more examples!