To determine the best Lewis structure for ammonia (NH₃), let's follow these steps in detail:
### Step 1: Count the valence electrons
First, determine the total number of valence electrons in the molecule.
- Nitrogen (N) is in group 15 of the periodic table and has 5 valence electrons.
- Hydrogen (H) is in group 1 and has 1 valence electron. There are three hydrogens, so the total number of valence electrons contributed by hydrogen is 3 \ 1 = 3.
Total valence electrons in NH₃ = 5 (from N) + 3 \ 1 (from H) = 8 valence electrons.
### Step 2: Draw the skeletal structure
Nitrogen is less electronegative than hydrogen and often serves as the central atom. Connect each hydrogen atom to nitrogen with a single bond.
[tex]\[
\text{H - N - H}
|
H
\][/tex]
Each single bond consists of 2 electrons, so connecting each hydrogen to nitrogen uses up 6 electrons (3 bonds \* 2 electrons per bond = 6 electrons).
### Step 3: Distribute remaining valence electrons
Starting at the central atom, we distribute the remaining electrons (8 - 6 = 2 electrons) to complete the octet rule where possible.
Nitrogen will get the remaining 2 electrons to complete its octet.
[tex]\[
H
|
H - N - H
|
(2 e^-)
\][/tex]
### Step 4: Verify the octet rule
Check that each atom has a full valence shell.
- Each hydrogen atom has 2 electrons (1 bond \ 2 electrons/bond), which is a full valence shell for hydrogen.
- Nitrogen has 8 electrons (3 bonds \ 2 electrons/bond + 2 lone pair electrons), which satisfies the octet rule for nitrogen.
### Step 5: Choose the best structure
The final Lewis structure for NH₃ should look like this:
[tex]\[
H
|
H - N - H
|
..
\][/tex]
Here, the pair of dots (..) represents the lone pair on nitrogen.
So, among the provided choices, the one that follows this arrangement is the best structure. If we look at each option:
```
H- H- H- H- None of these structures represent
I H N N- the correct Lewis structure for NH₃
N I I I
H -Z: -Z: -Z:
H I I I
Z Z N
I I
N
H
```
The correct representation is not clearly included in these symbol representations without the explanation. The structure:
```
H
|
H-N-H
. .
```
is closest to option C but best visualized following my step-by-step breakdown.
Thus, the Lewis structure for NH₃ must be considered in the text format with nitrogen at the center, a single bond with each hydrogen, and a lone pair of electrons on nitrogen.
