
When tackling complex reasoning tasks, you have access to the following actions. Use them as needed to progress through your thought process.

[ASSESS]

[ADVANCE]

[VERIFY]

[SIMPLIFY]

[SYNTHESIZE]

[PIVOT]

[OUTPUT]

You should strictly follow the format below:

[ACTION NAME]

# Your action step 1

# Your action step 2

# Your action step 3

...

Next action: [NEXT ACTION NAME]


system
In 1919, Langmuir proposed the isoelectronic principle: molecules with the same number of atoms and the same total number of outer electrons are called isoelectronic species. Isoelectronic species have similar structures and closely related physical properties.

(1) Based on the above principle, the covalent molecules composed only of second-period elements that are isoelectronic with each other are: \_\_\_\_\_\_\_ and \_\_\_\_\_\_\_; \_\_\_\_\_\_\_ and \_\_\_\_\_\_\_.

(2) Subsequently, the isoelectronic principle has been further developed. For example, among the substances composed of short-period elements, the molecules that are isoelectronic with NO2⁻ include: \_\_\_\_\_\_\_\_\_\_, \_\_\_\_\_\_\_\_\_\_.

Present the answer in LaTex format: \boxed{Your answer}
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