Using the conversion factor convert 1.56 ng nh3 to moles.

9.02×10⁻¹¹ mol NH₃

Explanation:

Convert nanograms to grams:

1.56 ng NH₃ × (1 g / 10⁹ ng) = 1.56×10⁻⁹ g NH₃

Convert grams to moles:

1.56×10⁻⁹ g NH₃ × (1 mol NH₃ / 17.3 g NH₃) = 9.02×10⁻¹¹ mol NH₃

a electronegativity decreases beacuse the size of nucleus is bigger.