Which of the following atoms is a cation?
A. 14 protons, 14 neutrons, 18 electrons
B. 34 protons, 45 neutrons, 36 electrons
C. 35 protons, 44 neutrons, 35 electrons
D. 82 protons, 125 neutrons, 78 electrons
Because it has more protons than electrons, this atom has a positive charge and can be classified as a cation. When a metal such as sodium reacts to become stable, it loses its valence electrons. At first, it is a neutral atom with 11 protons and 11 electrons. When it loses an electron, the number of protons does not change, and the atom has 11 protons and 10 electrons. Because there is one more positively charged proton, a cation forms. A cation is an ion with a net positive charge.
Therefore, the Correct Answer is D.