Which one of the formulas for ionic compounds below is incorrect?*1 point(a) SrCl2(b) Cs2S(c) AlCl3(d) Al3P2(e) CaSe

The incorrect formula among the given options is (d) Al3P2.

The correct formula for the ionic compound formed by Aluminum (Al) and Phosphorus (P) should be AlP.

Here's why:

1. Aluminum (Al) is in group 13 of the periodic table and therefore has 3 valence electrons. It tends to lose these 3 electrons to achieve a stable electron configuration, forming a +3 ion (Al3+).

2. Phosphorus (P) is in group 15 of the periodic table and therefore has 5 valence electrons. It tends to gain 3 electrons to achieve a stable electron configuration, forming a -3 ion (P3-).

3. When these ions combine to form an ionic compound, the charges should balance out. In this case, one Al3+ ion can balance one P3- ion, so the correct formula should be AlP, not Al3P2.