Element x has the highest first electron affinity in its period, the ground state electron configuration of its common is: [Kr] 5s2 4d10 5p6

Element Y is the second largest element in its period; its valence electron are in orbital(s) that have n= 6.

What is the most stable compound formed when elements X and Y are combined:_________

How'd you figure this question out?

I spent most of my time trying to figure out how all of that could be a compound of Xe until I realized it could NOT be and ion was the mission word/ I'm glad you confirmed that.

Do I assume you need an explanation of why it is BaI2?
The electron affinity increases from left to right in the table so you look at Kr, then you see that 4d10 5s2 5p6 adds to 18 so that element must be Xe. Since it's the ION, that makes the element {Kr] 4d10 5s2 5p5 and that is I and I has the highest electron affinity in that period. That's element X.
Y is the second largest element in the period with n = 6. Size decreases as you go from left to right in the periodic table (see link below) so Cs must the largest and that makes Ba the second largest. Y must be Ba. BaI2 follows from all of that.
http://crystalmaker.com/support/tutorials/crystalmaker/atomic-radii/index.html

Hope this helps.

Would you proof your post please. I think a word is missing "of its common .....is". I wonder if the missing word is ion. As posted element X makes no sense; in fact, [Kr]5s2 4d10 5p6 is Xe and that has the lowest electron affinity in its period. I've spent half an hour on this and realized something must be wrong with the post.

Yes it is "most common ion is: [Kr] 5s2 4d10 5p6".

I have also spent quite a long time trying to figure this question out.
The answer key said it's BaI2, which confused me more.

To determine the most stable compound formed when elements X and Y are combined, we need to consider their electron configurations and the tendency for elements to achieve a stable octet configuration.

For element X, the ground state electron configuration is given as [Kr] 5s2 4d10 5p6. This indicates that element X belongs to the noble gas family and has a total of 18 valence electrons. The noble gas electron configuration suggests that element X is highly stable and less likely to form compounds.

For element Y, we are told that its valence electrons are in orbital(s) with n = 6. The value of n indicates the principal quantum number, which determines the energy level of the electron orbitals. In terms of the periodic table, we can infer that element Y is located in Period 6.

Considering that element X has a higher first electron affinity in its period, it implies that element X readily gains an electron to achieve a stable electron configuration. On the other hand, element Y being the second largest element in its period suggests that it may be more likely to lose electrons to form compounds.

Now, to determine the most stable compound formed when elements X and Y are combined, we need to consider their valences and tendency to achieve a stable electron configuration. Since element X readily gains an electron and element Y is more likely to lose electrons, the most stable compound formed when elements X and Y are combined would be their 1:1 compound, where element X gains an electron from element Y.

Thus, the most stable compound formed when elements X and Y are combined would be XY, where element X gains an electron from element Y.