Which of the following weighs the least?
A. 2g of nitrogen (at. mass = 14)
B. 3×10^23 atoms of C (at. mass = 12)
C. 1 mole of S (at. mass = 32)
D. 7 g silver (at. mass = 108)

To determine which option weighs the least, we need to calculate the mass in grams of each option. Here's the approach:

### Option A: 2g of Nitrogen (atomic mass = 14)
The mass is directly given as 2g.

### Option B: \( 3 \times 10^{23} \) atoms of Carbon (atomic mass = 12)
We first need to determine the mass of this number of carbon atoms. The atomic mass of carbon is 12 grams per mole.

1 mole of carbon atoms contains \( 6.022 \times 10^{23} \) atoms (Avogadro's number).

Thus, the mass of \( 3 \times 10^{23} \) atoms of carbon is:
\[
\text{Mass} = \frac{3 \times 10^{23}}{6.022 \times 10^{23}} \times 12 \text{ g}
= 6 \text{ g}
\]

### Option C: 1 mole of Sulfur (atomic mass = 32)
1 mole of sulfur weighs 32 grams.

### Option D: 7g of Silver (atomic mass = 108)
The mass is directly given as 7g.

### Conclusion
- Option A: 2g
- Option B: 6g
- Option C: 32g
- Option D: 7g

The least mass is **Option A: 2g of Nitrogen**.

Thus, the correct answer is **A. 2g of nitrogen**.