An atom has nine protons and ten electrons. This makes it: An alpha particle
Neutrally charged
An ion
A cathode ray
Nonstoichiometric

C: Ion

Explanation:

We are told that the atom has;

9 protons

10 electrons.

Now, in chemistry, when number of electrons(negative) is more than number of protons(positive), we say that the atom is negatively charged.

Now, looking at the options;

- alpha particles have 2 protons and 2 neutrons and so it is not correct

- for an atom to be neutrally charged, number of protons must be equal to number of electrons. Thus it is not correct.

- For an atom to be an ion, it means that there is an unequal amount of electrons and protons. If the atom has more electrons than protons, it is called anion(negative ion) but if it has less electrons than protons, it is called cation(positive ion).

Thus, option C is the correct answer.