Ionic Bonds & Ionic Compounds

• Types of ions– Monatomic ions - ions formed from a single atom. • Ca2+, K+, Al3+, Cu+, Cu2+, Fe2+, Fe3+, Cl-, O2-, N3-

– Polyatomic ions - ions formed from multiple atoms• NH4

+, CO32-, SO42-, OH-, PO4

3-

Monatomic ions

• Monatomic ions - ions formed from a single atom. – Metals form cations and retain their name – Some transition metals can form more that one cation (Cu+, Cu2+, Fe2+,

Fe3+) • are named after their charge copper, copper II, iron II & iron III

– Non - metals form anions (negative charge) are renamed with the suffix -ide (Cl - chlorine, Cl- - chloride)

Polyatomic ions

• Polyatomic ions - ions formed from multiple atoms – The atoms of a polyatomic ion are contain covalent bonds (shared

electrons) but form an ion that participates in ionic bonding – Each polyatomic ion remains intact when forming ionic compounds

Binary Ionic Compounds

• Binary ionic compounds are formed from the union of 2 ions (cation & anion). The bond is relatively strong and the ratios of cations to anions is related to the charge on each ion.– The ionic compound is named after its components - NaCl is sodium

chloride – The empirical formula (chemical formula) tells us about the exact

numbers and ratios in the ionic compounds. The empirical formula only lists elements in their reduced quantities.

Li+ + O2- a 2Li+O2- a Li2O Lithium oxide

Ca2++ 2Cl- a CaCl2 Calcium chloride

Criss-Cross Method

• The criss-cross method is used to balance ionic charges when forming ionic compounds.– Simply put the charge (superscript number) as the

opposite atom's subscript number. Then reduce.

Mg2+ + S2- a Mg2+S2-a Mg2S2a MgS Magnesium sulfide

(the ratio of the subscripts is reduced)

K+ + N3- a K+N3-a K3N Potassium nitride

(the #1 is not written as a subscript)

AL3++ O2- a AL3+O2- a AL2O3 Aluminum oxide