First, we will find out if the element is fluorine or neon. The atomic number of each element are also the number of protons in an ion. Fluorine has an atomic number of 9, which means a fluorine ion has 9 protons. Neon has an atomic number of 10, which means a neon ion has 10 protons.
So we can cross out D.
Next, we can figure out a charge of an ion by looking at protons and electrons. Neutrons doesn’t matter since they’re neutral and only contribute to the mass. Protons and positive and electrons are negative. It’s like doing kindergarten math. John has 9 apples and he eats 10 (I know it’s not possible), how many apples does he have left? The answer is -1. The number of electrons are greater than the number of protons, so the ion is negative.
The answer is therefore C. A negatively charged fluoride ion.