Moles of N³⁻ = 4.2g / 14g/mol = 0.3 mol. A neutral nitrogen atom has 5 valence electrons. A nitride ion (N³⁻) has 5 + 3 = 8 valence electrons. Total valence electrons = 0.3 mol × 8 electrons/ion × N_A ions/mol = 2.4 N_A. [cite: 381, 387, 388, 389, 390]