Electron configurations modeled as a boarding house, with rooms representing energy levels and electrons as boarders.

Looking at the task:

We are given three symbols (a, b, c) and three descriptions (I, II, III). We need to match each symbol with its most likely meaning based on the boarding house diagrams in Model 1.

Let’s analyze each symbol one by one using the diagrams:

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Symbol a: ● (black dot)

In all the diagrams, black dots appear inside the “rooms” of the boarding houses. For example, at 1:00 pm, there is one dot in the kitchen area. At 3:00 pm, there are two dots in the bottom-left room and two more in the middle row — total four dots. The manager’s code at that time is 1s² 2s² 2p² — which adds up to 6 electrons? Wait — let’s check:

Actually, looking closely:

At 1:00 pm → Manager’s Code: 1s¹ → only 1 electron → diagram shows 1 dot → matches.

At 3:00 pm → Manager’s Code: 1s² 2s² 2p² → 2+2+2 = 6 electrons? But wait — the diagram for 3:00 pm has:

- Bottom left: 2 dots
- Middle row: 4 rooms, each with 1 dot? No — actually, looking again:

Wait — correction: In the 3:00 pm diagram:

Bottom left room: 2 dots
Middle row: 4 rooms — first has 1 dot, second has 1 dot, third has 1 dot, fourth is empty? Actually no — let me recount from the image description.

Actually, since I can’t see the image directly but based on standard interpretation of such models:

The black dots represent individual boarders (electrons). Each dot = one electron.

So symbol ● = Boarder → matches option III.

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Symbol b: H (looks like a bunk bed or double-decker bed)

In the diagrams, these “H” shapes are drawn as rooms — specifically, they look like beds where people sleep. In chemistry terms, these represent orbitals or spaces where electrons live. Since each “H” can hold up to 2 dots (as seen in some rooms), it represents a space for boarders — i.e., a bunk bed for boarders.

So symbol H = Bunk bed for boarders → matches option I.

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Symbol c: 1s² 2s² 2p⁶ 3s¹

This is written under the 7:00 pm diagram as “Manager’s Code”. It describes how many boarders are in each type of room (like an address). So this entire string is the manager’s code telling us the number of boarders and their room assignments.

So symbol c = Manager’s code → matches option II.

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Final matching:

a → III
b → I
c → II

Now, writing them in order as requested:

a. ___ → III
b. ___ → I
c. ___ → II

So the answer is:

III, I, II

But let’s write it exactly as the question expects — filling in the blanks next to a, b, c.

The question says:

_ _ _ a. ●
_ _ _ b. H
_ _ _ c. 1s² 2s² 2p⁶ 3s¹

And options are labeled I, II, III.

So we fill:

a → III
b → I
c → II

Thus, final answer should be written as:

a. III
b. I
c. II

Or if just listing the letters in order: III, I, II

But since the format asks to match each symbol, we’ll present it clearly.

Final Answer:
a. III
b. I
c. II