An Element's Most Stable Ion Forms an Ionic Compound with Chlorine

Multiple Choice

An element's most stable ion forms an ionic compound with chlorine having the formula XCl₂. If the ion of element X has a mass of 89 and 36 electrons, what is the identity of the element, and how many neutrons does it have?

A) Kr, 53 neutrons
B) Kr, 55 neutrons
C) Se, 55 neutrons
D) Sr, 51 neutrons
E) Rb, 52 neutrons