An element’s most stable ion forms an ionic compound with bromine, having the formula XBr2. If the ion of element "X" has a mass number of 230 and has 86 electrons, what is the identity of the element, and how many neutrons does it have?

The element X having a mass number of 230 and has 86 electrons is radium and has  142 neutrons.

An atom is composed basically of electrons, protons and neutrons. In a neutral atom, the number of protons and electrons are equal. The number of neutrons is the difference between the mass number and the number of protons (atomic number).

Since we know that the ion of the element X has 86 electrons and the compound formed is XBr2, it then means that neutral X has 88 electrons.

The number of electrons in the neutral atom is the same as the number of protons or atomic number. An element can be identified by its atomic number. The element having atomic number 88 is radium.

The number of neutrons is obtained as;

Mass number - atomic number

230 - 88 = 142 neutrons

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88

Explanation:

The ion has a charge of 2+, therefore the number of neutrons it possess is 86+2

which equals 88