Final answer:
To arrange the elements S, P, Cl, and Ca in order of increasing electron affinity, we need to consider their positions in the periodic table and the trends in electron affinities. The correct order is: Ca < Cl < P < S.
Step-by-step explanation:
The electron affinity (EA) is the energy change associated with the addition of an electron to an atom or ion in the gaseous state. A higher electron affinity value indicates a stronger attraction for the electron. To arrange the elements S, P, Cl, and Ca in order of increasing electron affinity, we need to consider their positions in the periodic table and the trends in electron affinities.
Electron affinities generally increase from left to right across a period and decrease down a group. The atomic number and electron configuration of the elements can also affect their electron affinities.
In this case, the elements are: Ca (atomic number 20), Cl (atomic number 17), P (atomic number 15), and S (atomic number 16). Since Ca is a metal and is located far to the left of the periodic table, it has the lowest electron affinity. Cl is a nonmetal and is to the right of Ca, so its electron affinity is higher than that of Ca. P is further to the right than Cl, so its electron affinity is higher than that of Cl. Finally, S is the furthest to the right among these elements, so it has the highest electron affinity. Therefore, the correct order is: Ca < Cl < P < S.