Question

1. how do you determine the charges on the ions in an ionic compound?

Explanation:

• For metals in main groups (Groups 1 - 3): They lose electrons to form cations. Group 1 metals form +1 ions (e.g., \(Na^+\)), Group 2 metals form +2 ions (e.g., \(Mg^{2+}\)), and Group 3 metals form +3 ions (e.g., \(Al^{3+}\)).
• For non - metals in main groups (Groups 5 - 7): They gain electrons to form anions. Group 5 non - metals form - 3 ions (e.g., \(N^{3 -}\)), Group 6 non - metals form - 2 ions (e.g., \(O^{2 -}\)), and Group 7 non - metals form - 1 ions (e.g., \(Cl^-\)).
• For transition metals: Their ion charges can be determined from the formula of the ionic compound. For example, in \(FeCl_2\), since \(Cl^-\) has a - 1 charge and there are two \(Cl^-\) ions, the iron ion (\(Fe\)) has a + 2 charge (\(Fe^{2+}\)). In \(FeCl_3\), the iron ion has a + 3 charge (\(Fe^{3+}\)) as there are three \(Cl^-\) ions.
• For polyatomic ions: Their charges are known values. For example, the sulfate ion (\(SO_4^{2 -}\)) has a - 2 charge, the ammonium ion (\(NH_4^+\)) has a + 1 charge. In an ionic compound like \((NH_4)_2SO_4\), we use the known charges of the polyatomic ions.

Answer:

To determine the charges on ions in an ionic compound:

• For main - group metals (Groups 1 - 3), use their group number (Group 1: +1, Group 2: +2, Group 3: +3).
• For main - group non - metals (Groups 5 - 7), use \(8 - \text{group number}\) (Group 5: - 3, Group 6: - 2, Group 7: - 1).
• For transition metals, calculate based on the formula (using the charge balance with known non - metal or polyatomic ion charges).
• For polyatomic ions, use their known standard charges.