An element forms an ionic compound with bromine having the formula XBr. If the mass number of the element X is 41 and the ion has 18 electrons, what is the element X and how many neutrons does it have?

X is calcium and it has 21 neutrons

Explanation:

Calcium 41 is an isotope of calcium with mass number of 41 and atomic number of 20

Number of neutrons = mass number - number of electrons

The number of electrons is the same as the atomic number of the element (calcium)

Number of neutrons = 41 - 20 = 21