The periodic chart says that f can take on a charge of - 1 to become f-1, how does this happen?

These electrons can either be lost to another atom, or the valence shell may have room ... want to gain or lose an electron, it will never happen with an isolated atom ... that make it very easy to determine the charge directly from the periodic table ... He0. Li +. Be+2. B+3. C-4. N-3. O-2. F-. Ne0. Na+. Mg+2. Al+3. Si-4. P-3. S-2.