The group number, number of valence electrons, and valency of an element with atomic number 15, respectively, are:

Question

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Strategy:
 Phosphorus () serves as the basis. Determine its group by adding 10 to the number of -electrons (for -block), its valence electrons by counting the outermost shell, and its valency based on octet completion.

Step 1: Write electronic configuration
Phosphorus (): .
- Group: 15 (-block).
- Valence electrons:  electrons.
- Valency: It needs 3 electrons to complete its octet .

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