Fluorine is a Group 7 element, so in order to get an octet of electrons, it needs one more. So fluorine will gain one electron to become fluoride. (F-)
in a normal F- ion there are 10 electrons total (but 8 in the outer energy level)
It will lose 2 to form Sr2+
Krypton is a noble gas and generally does not gain or lose electrons.
In phosphene it gain 4 electrons. Phosphate lose 4 electrons