The electron affinity values(in KJ mole^-1) of three halogens x, y and z are respectively -349, -333 and -325. Then x, y and z respectively are

The electron affinity is defined as the energy change that occurs when a neutral atom in the gas phase gains an electron to form a negatively charged ion.

The given electron affinity values of the halogens x, y, and z are:

x = -349 kJ/mol  y = -333 kJ/mol  z = -325 kJ/mol

The electron affinity  decreases as we move down a group in the periodic table.

Chlorine has a larger atomic size and more protons in its nucleus than fluorine. This means that the valence electrons in chlorine are farther away from the nucleus and experience a weaker attractive force compared to the valence electrons in fluorine, which are closer to the nucleus and experience a stronger attractive force.

As a result, when an electron is added to a chlorine atom, the electron is more easily accommodated in the larger, more diffuse outer shell of the chlorine atom, and less energy is required to add the electron. In contrast, adding an electron to the smaller, more tightly bound outer shell of the fluorine atom requires more energy due to the stronger attractive force of the nucleus for its valence electrons.

Therefore, chlorine has a higher electron affinity than fluorine.

So, the halogens x, y, and z respectively are  Cl, F, and Br.