As the first five elements in Group 15 are considered in order of increasing atomic number, first ionization energy increases, then decreases decreases, then increases decreases increases

Answer: the first ionization energy decreases.

Justification:

1) The group 15 is formed by N, P, As, Sb, Bi, and Mc.

2) The first ionization energy is defined as the energy needed to remove an electron from the neutral atom in the gas state.

3) The elements of the group 15 have the following general electron configuration for the valence shell: ns² np³. Where n is the principal quantum number (the same number of the row in which the element is).

4) As you go down in the group, n increases, and the valence electrons are further away of the nucleous, meaning that those electrons are lessen attracted to the nucleous.

Consequently, as you go down in the group, the electrons will be removed more easily, i.e less energy will be required to get them removed.

5) That permits you to predict this order in the first ionization energies: N > P > As > Sb > Bi > Mc.

And that agrees with the data that you can find in a table of first ionization energies.

Final answer:

As atomic number increases, first ionization energy in Group 15 elements initially rises due to increasing nuclear charge, then decreases because of larger atomic radius, and finally increases again due to stronger attraction between cations and remaining electrons.

Explanation:

The first ionization energy refers to the energy necessary to remove an electron from a neutral atom. As we consider the first five elements in Group 15 in order of increasing atomic number, there's a trend that emerges regarding first ionization energy. Initially, the ionization energy increases. This is due to an increasing effective nuclear charge that tightens the hold on the electrons, making it more energy-consuming to remove them.

Then, there's a decrease in ionization energy. This is caused by the additional energy level of electrons, which increases atomic radius and reduces the impact of nuclear charge - it's easier to remove an electron from a larger, higher-energy orbital. Following this, the ionization energy starts increasing again. This is because unrelated to size, it becomes increasingly difficult to remove additional electrons which have a greater electrostatic attraction to the cation that's formed.

Learn more about First Ionization Energy here:

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