Explanation:

Ionization energy:
Ionization energy is the energy required to remove an electron from an atom or ion in the gaseous state. It is a measure of the strength of the attraction between the electrons and the nucleus of an atom. Increased ionization energy indicates a stronger attraction, while decreased ionization energy indicates a weaker attraction.

Ionization energy and group:
When moving down a group in the periodic table, the ionization energy generally decreases. This is due to the following factors:

1. Increasing atomic size:
As you move down a group, the atomic size increases. This is because additional energy levels or shells are being added. The increased distance between the nucleus and the outermost electrons weakens the attraction between them, making it easier to remove an electron and decreasing the ionization energy.

2. Increased shielding effect:
The addition of energy levels or shells also results in an increased number of inner electrons. These inner electrons shield the outer electrons from the full attraction of the nucleus. As a result, the outer electrons are less tightly held, making it easier to remove them and decreasing the ionization energy.

3. Decreased effective nuclear charge:
The effective nuclear charge is the net positive charge experienced by an electron in an atom. As you move down a group, the number of protons in the nucleus increases, but the increased shielding effect outweighs the increase in protons. This leads to a decrease in the effective nuclear charge, making it easier to remove an electron and decreasing the ionization energy.

Formation of anions:
An anion is a negatively charged ion formed when an atom gains one or more electrons. The addition of electrons to an atom requires energy, as it goes against the natural tendency of the atom to lose electrons and achieve a stable electron configuration. Therefore, the energy required to form an anion is not the ionization energy, but rather the electron affinity or the energy change associated with adding an electron to a neutral atom.

Conclusion:
In conclusion, the statement that ionization energy decreases down the group and is the energy required to form an anion is incorrect. Ionization energy decreases down the group due to increasing atomic size, increased shielding effect, and decreased effective nuclear charge. The energy required to form an anion is the electron affinity, not the ionization energy.