* Protons determine the element: An atom with 6 protons is a carbon atom (C).

* Electrons and charge: A neutral carbon atom has 6 electrons. Since this atom has 4 electrons, it has lost 2 electrons (6 - 4 = 2). Losing electrons creates a positive charge.

* Ion notation: The ion notation is C²⁺.

Explanation:

* C represents the element carbon.

* ²⁺ indicates a +2 charge, meaning the atom has lost two electrons.