[MahdiKordian]

Summary

• Fix the index used to access the fourth item in the pressures list.
• Replace "zeroth" with "first" in the list and string examples.
• Correct the string indexing example so the third character of carbon is accessed with element[2].
• Update the expected outputs to match the corrected examples.

Validation

• Checked the expected values and outputs against Python's zero-based indexing.
• git diff --check completed without errors.

Closes #732

[github-actions]

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