Question

The atomic number of an element X is 8 and that of element Y is 12. Write down the symbols of the ions you would expect to be formed from their atoms.

Answer 1

Element X is oxygen (atomic number 8). Oxygen needs two more electrons to complete its noble gas configuration. The element Y is magnesium (atomic number 12). Magnesium has two extra electrons than are needed to achieve a stable configuration. Hence, magnesium donates two electrons to the oxygen atom to attain a stable configuration.
So, Mg becomes Mg²⁺ and O becomes O^2- as ions.