It called cation, Well, When an atom gains or loses an electron, it
attains a net charge and becomes an ion. When electrons are lost, the
resulting ion is called cation and when electrons are gained, the
resulting ion is called an anion. So, Cations have a net positive
charge, while anions have a net negative charge. it is true.
The mass number goes on top, and the atomic number goes on bottom.
Therefore, the answer is C:
40
K
19
