1(viii)
The diagram given below shows the bonding in the covalent molecule AB2.
Which option represents the correct electronic configuration of atoms A and B before combining together to form the above molecule?
| A | B | |
|---|---|---|
| 1 | 2, 4 | 2, 8, 6 |
| 2 | 2, 4 | 2, 8, 7 |
| 3 | 2, 8 | 2, 8, 8 |
| 4 | 2, 6 | 2, 8, 7 |
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| 4 | 2, 6 | 2, 8, 7 |
Reason
- Atom A has six valence electrons (configuration 2, 6) and therefore needs two more electrons to complete its octet.
- Each atom B has seven valence electrons (configuration 2, 8, 7) and needs one additional electron to attain a stable, noble-gas configuration.
- In the AB2 molecule, atom A forms a single covalent bond with each of two B atoms. Through this sharing, atom A gains two electrons (one from each B), while each B gains one electron from A, so all three atoms achieve an octet.