What is the charge on a fluorine ion? explain answer plz

-1 

An ion is an atom which has gained or lost electrons. 
Atoms want to have full outer shells of electrons. 
Electrons are negative. 
Fluorine has 7 electrons in its outer shell. When it gains one to fill its shell it will be made negative.
Thus the charge of a fluorine ion is -1 

Tolerance to high levels of salinity

If a hydrogen atom is neutral, it must also have  one electron. an oxygen atom (o) has an atomic number of eight (8). this means a neutral oxygen atom has eight protons and eight electrons. the element actium (ac) has an atomic number of 89, so it has 89 protons and 89 electrons in a neutral atom