How do you draw the Lewis Structure for NH4Cl, which has 17 valence electrons?
The correct answer and explanation is:
Sure! Let’s go through drawing the Lewis structure for NH4Cl (ammonium chloride) step by step.
Step 1: Count total valence electrons
- N (Nitrogen): Group 15 → 5 valence electrons
- H (Hydrogen): Group 1 → 1 valence electron × 4 = 4 electrons
- Cl (Chlorine): Group 17 → 7 valence electrons
Total valence electrons = 5 (N) + 4 (H) + 7 (Cl) = 16 valence electrons
Important note: NH4Cl is actually an ionic compound, consisting of NH4⁺ (ammonium ion) and Cl⁻ (chloride ion), so the Lewis structure represents these ions separately, not a single molecule.
- NH4⁺ ammonium ion (positive charge, so 1 electron less than neutral)
- Cl⁻ chloride ion (negative charge, so 1 electron more than neutral)
Step 2: Adjust valence electrons for ions
- NH4⁺: 5 (N) + 4 (H) – 1 (positive charge) = 8 valence electrons
- Cl⁻: 7 (Cl) + 1 (negative charge) = 8 valence electrons
Step 3: Draw Lewis structure for NH4⁺
- Nitrogen is central atom.
- Attach four hydrogen atoms to nitrogen by single bonds.
- Each N-H bond represents 2 electrons; total 4 bonds × 2 = 8 electrons, which uses all valence electrons for NH4⁺.
- Nitrogen has a formal positive charge because it has 4 bonds (one more than its normal valence of 3).
NH4⁺ looks like:
H
|
H — N — H
|
H
with a +1 charge on nitrogen.
Step 4: Draw Lewis structure for Cl⁻
- Chlorine atom with 3 lone pairs (6 electrons) plus one extra electron for the negative charge.
- Total of 8 valence electrons around Cl (octet complete).
Cl⁻ looks like:
..
: Cl :
..
with a -1 charge on chlorine.
Step 5: Combine NH4⁺ and Cl⁻
- NH4⁺ and Cl⁻ are held together by ionic bonds.
- No covalent bonds between NH4⁺ and Cl⁻.
- The overall compound NH4Cl is neutral because +1 and -1 charges cancel out.
Summary explanation:
- NH4Cl is an ionic compound made of ammonium ion (NH4⁺) and chloride ion (Cl⁻).
- The ammonium ion has 8 electrons around nitrogen from 4 single N-H bonds, with a positive charge due to 1 fewer electron.
- The chloride ion has 8 electrons (including an extra electron for the negative charge) completing its octet.
- These ions interact via ionic attraction, not covalent bonding.
- Total valence electrons counted depends on the ionic charges, so for the whole compound, valence electrons are split into the ions accordingly.