When the transfer occurs, sodium’s valence shell is empty, making the next ring in the valence shell, which is full.
What is happening? The one valence electron from potassium is transferred to the iodine. Both become stable with now full outer rings. Potassium becomes positively charged (+1: lacking one electron) and Iodine becomes negatively charged (-1: one extra electron).
Multiple ions The two valence electrons from magnesium are transferred, one to each chlorine. All three become stable with now full outer rings. Magnesium becomes positively charged (+2: lacking two electrons) and each chlorine becomes negatively charged (-1: one extra electron).
Steps for Writing Ionic Formulas 1.Write the symbols for the ions with the cation first, and anion second. 2.Balance the charges by inserting subscripts. There must be equal numbers of positive and negative charges to balance out to zero overall charge. 3. Write the chemical formula, indicating with subscripts how many of each ion are needed to make a neutral compound.
Polyatomic Ions Polyatomic ion – multiple atoms covalently bonded together which, as a group, have an overall charge to become stable The group will lose or gain electrons to become stable. Act as a unit
You cannot change subscripts of the polyatomic ion, but can have multiple of the unit. Examples: Hydroxide OH - Sulfate SO 4 2- Phosphate PO 4 3-
This ion cannot be changed, but you can have more than one of the ion. Use parentheses and a subscript outside the parentheses to balance charges. Beryllium chlorate Be 2+ ClO 3 - Be 2+ ( ClO 3 - ) 2