Draw the Lewis Structure for NI3.
The Correct Answer and Explanation is:
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Lewis Structure for NI₃ (Nitrogen Triiodide)
Here’s the correct Lewis structure for NI₃:
mathematicaCopyEdit I
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I — N — I
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- Nitrogen (N) is the central atom.
- Each iodine (I) atom is bonded to nitrogen with a single covalent bond.
- Each iodine has 3 lone pairs (6 electrons).
- Nitrogen has 1 lone pair (2 electrons) after forming 3 bonds.
Explanation
Nitrogen triiodide (NI₃) is a covalent compound consisting of one nitrogen atom and three iodine atoms. To draw its Lewis structure, we follow the steps of counting valence electrons, arranging atoms, and satisfying the octet rule.
- Count the total valence electrons:
- Nitrogen (Group 15) = 5 valence electrons
- Iodine (Group 17) = 7 valence electrons × 3 = 21
- Total = 5 + 21 = 26 valence electrons
- Choose the central atom:
- Nitrogen is less electronegative than iodine, so it goes in the center.
- Form single bonds:
- Connect each iodine to nitrogen with a single bond. This uses 3 bonds × 2 electrons = 6 electrons.
- Distribute remaining electrons:
- 26 − 6 = 20 electrons left
- Place 6 electrons (3 lone pairs) on each iodine (3 × 6 = 18)
- Place the remaining 2 electrons as a lone pair on nitrogen
- Check octets:
- Each iodine has 1 bond + 3 lone pairs = 8 electrons (octet satisfied)
- Nitrogen has 3 bonds + 1 lone pair = 8 electrons (octet satisfied)
- Molecular shape and polarity:
- NI₃ has a trigonal pyramidal shape due to the lone pair on nitrogen.
- The molecule is polar because of the asymmetrical shape and polar N–I bonds.
In summary, the Lewis structure for NI₃ shows nitrogen with three single bonds to iodine atoms and one lone pair, and each iodine with three lone pairs. The molecule’s geometry and electron distribution make it unstable and highly reactive, especially in its solid form, where it can be explosively sensitive.
