PSE Advent Calendar 2024 (Day 18): A sweet & short expected chemistry Christmas puzzle

Question

<sub>This puzzle is part of the Puzzling Stack Exchange Advent Calendar 2024. The accepted answer to this question will be awarded a bounty worth 50 reputation.

< Previous Door Next Door ></sub>

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To get the green checkmark $\color{green}✓$:

• Answer the question
• Show the solution process taken to solve the puzzle

Question:

What does the following represent? The answer should be a (REDACTED)-word phrase.

(1) 1s² 2s² 2p⁶ 3s²
(2) 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶
(3) 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹
(4) 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p³
(5) 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 5d¹ 4f¹¹

_____    _____    _____    _____    _____    _____  !
(1)-g    (5)+r     (3)     (2)-e    (1)-g     (4)

Answer 1

These are

atoms, represented by their electron configurations. For example, the first is magnesium, which has two electrons in the 1s orbital, two electrons in the 2s orbital, six electrons in the 2p orbital, and two electrons in the 3s orbital. So we have:

(1) Magnesium (12 total electrons)
(2) Xenon (54 total electrons)
(3) Yttrium (39 total electrons)
(4) Arsenic (33 total electrons)
(5) Erbium (68 total electrons)

The next logical thing to do is, of course,

replace each element with its symbol:

(1) Mg
(2) Xe
(3) Y
(4) As
(5) Er

Now let's focus on those blanks...

We have two that say (1)-g. If we replace (1) with Mg, then we have Mg-g, which would of course be M. That seems promising, so let's continue:

Mg-g = M
Er+r = Err
Y = Y
Xe-e = X
Mg-g = M
As = As

So the final message is

MErrY XMAs!