Final answer:
The electron affinity (z) in terms of electronegativity (x) and ionisation potential (y) cannot be accurately determined from the given options without additional information, as the relationship is not direct and requires specific formulations.
Step-by-step explanation:
Understanding the relationship between electronegativity (x), ionisation potential (y), and electron affinity (z) is essential for comprehending chemical bonding and periodic trends. Electronegativity is a measure of how strongly an atom attracts electrons in a bond, while ionization potential is the energy required to remove an electron from an isolated atom or ion. The electron affinity refers to the energy change when an electron is added to an atom, which can be either negative or positive depending on the element.
In terms of x and y, there is no direct equation that relates x, y, and z accurately due to the different units and the fact that electronegativity is a derived value and not directly measurable. However, electronegativity is known to be a function of both the atom's ionization energy and its electron affinity. Typically, elements with high electronegativity also have high ionisation potentials and more negative electron affinities, reflecting their tendency to attract and hold onto electrons.
Based on the provided options and taking into account that these are not direct relationships, no option correctly represents the expression for z in terms of x and y. Therefore, the correct answer cannot be determined from the given options without making assumptions or having additional information. To find a correct expression, detailed knowledge of the specific relationships and mathematical formulations used to derive these properties is necessary.