H3 Chemistry 9813 · Study focus: H3 Chemistry: Distinguish atomic and molecular orbitals
H3 Chemistry: Distinguish atomic and molecular orbitals
Start from the governing chemical model, test it against evidence, then transfer the reasoning to an unfamiliar case.
Your success criteria
- Distinguish atomic and molecular orbitals
- Use named chemical evidence.
- Transfer the governing reason to an unfamiliar case.
Orientation and prerequisite retrieval
An atomic orbital is centred on one nucleus, whereas a molecular orbital extends over the bonded nuclei.
Two hydrogen 1s atomic orbitals supply the basis functions for the two H2 molecular orbitals.
Definitions and exact language
An electron assigned to a molecular orbital is described over the molecule rather than owned by one atom.
Atomic-orbital labels identify an atom and shell; molecular-orbital labels also state molecular symmetry.
A molecular orbital may receive unequal contributions from different atoms without becoming an atomic orbital.
The number of molecular orbitals formed equals the number of atomic orbitals combined.
Text alternative: Text alternative: Electron density between two nuclei can be represented by a molecular orbital spanning both centres. The decisive distinction is the orbital's spatial domain and molecular combination, not merely its letter label.
Detailed molecular explanation
A molecular orbital may receive unequal contributions from different atoms without becoming an atomic orbital.
The number of molecular orbitals formed equals the number of atomic orbitals combined.
Worked leaf-specific case
Electron density between two nuclei can be represented by a molecular orbital spanning both centres.
A one-centre orbital remains an atomic orbital even when another atom approaches before combination.
- A candidate writes, “A molecular orbital belongs to whichever atom contributes most strongly.” Which correction should replace it?
Open the feedback checkpoint after attempting
- An atomic orbital is centred on one nucleus, whereas a molecular orbital extends over the bonded nuclei.
Guided evidence check
Molecular-orbital wavefunctions are combinations of compatible atomic-orbital wavefunctions.
A diagram should draw AO levels at the sides and resulting MO levels in the molecular centre.
- Which labelled diagram, spectrum or calculation would most directly disprove “The label 1s proves that an orbital is molecular.”?
Open the feedback checkpoint after attempting
- Atomic-orbital labels identify an atom and shell; molecular-orbital labels also state molecular symmetry.
Independent transfer
Occupation of an MO is shown on a molecular energy level, not by placing the same electron in two AOs.
The decisive distinction is the orbital's spatial domain and molecular combination, not merely its letter label.
- Design a specific chemical check that would expose the error in “Electron density between nuclei must be represented by two separate atomic orbitals only.”
Open the feedback checkpoint after attempting
- Electron density between two nuclei can be represented by a molecular orbital spanning both centres.
Misconception repair
Misconception: An MO electron simultaneously occupies two independent AO energy levels.
Repair: Occupation of an MO is shown on a molecular energy level, not by placing the same electron in two AOs.
- Write leaf-specific feedback for the misconception “An MO electron simultaneously occupies two independent AO energy levels.”
Open the feedback checkpoint after attempting
- Occupation of an MO is shown on a molecular energy level, not by placing the same electron in two AOs.
Practice, unseen assessment, re-test and next step
Complete the diagnostic questions, review the feedback, then attempt the final check.
After delayed re-test, continue to Classify bonding, antibonding and nonbonding orbitals at /learning/h3-molecular-orbitals-bonding-character-lesson.html.
- Review the feedback for each diagnostic question, then attempt the final check.
Open the feedback checkpoint after attempting
- Before moving on, state this boundary: The decisive distinction is the orbital's spatial domain and molecular combination, not merely its letter label.