The first ionization energy of an element is the energy required to remove an electron from a gaseous atom of an element to produce a +1 ion: M(g) + energy ---> M ^(+) (g) + e -
How do you think the activity of an element ought to be related to its first ionization energy? Predict a decreasing order of reactivity of the above elements based on their first ionization energies.

The higher the ionization energy, the lower the reactivity.

Explanation:

Hello there!

In this case, according to the given information, it turns out possible for us to draw a conclusion about the relationship between ionization energy and reactivity, by bearing to mind that the former is the energy the atom needs to lose its electron, this means that the higher the energy, the more difficult is for the atom to do so.

Based on the aforementioned, since the reactivity is related to how likely an atom undergoes a chemical change by losing or gaining electrons, we can say that the reactivity decreases as the ionization energy increase as, again, it is more difficult for the atom to have an excited state allowing its chemical interaction with another substance.

Unfortunately, the "above elements" where not given, so this part could not be solved, however, you can use the attached periodic trend for ionization energy to figure out the correct order, by keeping in mind the previous reasoning.

explanation:

let the different atoms be x and y. each with four protons and same mass will be represented as follows.

mass number is number of protons + number of neutrons.

            and  

since, it is given that one has a negative charge while the other is neutral. therefore, there will be increase in number of protons and the atom will be represented as follows.

according to periodic table, mass number of beryllium is 9 and it has atomic number 4 so, the atoms will be and .  

the protons and neutrons will be located inside the nucleus whereas the electrons will be revolving around the nucleus.