Which of the following is the correct chemical formula for barium nitride?

• A. Ba3N2
• B. Ba2N3
• C. BaN2
• D. Ba(NO3)2

Answer: (A)

Verified step by step guidance

1. Step 1: Identify the ions involved. Barium is a metal in Group 2 of the periodic table, so it forms a cation with a charge of +2, written as \(\mathrm{Ba^{2+}}\).
2. Step 2: Determine the charge of the nitride ion. Nitrogen typically gains three electrons to form the nitride ion with a charge of -3, written as \(\mathrm{N^{3-}}\).
3. Step 3: Use the crisscross method to balance the charges between the cation and anion. The total positive charge must balance the total negative charge in the compound.
4. Step 4: Cross the charges to become subscripts for the opposite ion: the charge of \(\mathrm{Ba^{2+}}\) (2) becomes the subscript for nitrogen, and the charge of \(\mathrm{N^{3-}}\) (3) becomes the subscript for barium, giving the formula \(\mathrm{Ba_3N_2}\).
5. Step 5: Verify that the total positive and negative charges balance out: 3 barium ions at +2 each give +6, and 2 nitride ions at -3 each give -6, confirming the formula \(\mathrm{Ba_3N_2}\) is correct.