Ionic Compounds

Learning Goals

• Describe the relationship between chemical formulae, composition, and names of ionic compounds

• Describe the properties of ionic compounds

Warm-Up

1. Why do we name objects, people, pets, elements, etc.?

2. Do all names stay the same? Do your names always stay the same?

Ionic Bonding• Metals– Electron donors– Donate their valence

electrons to become a positive ion (cation)

• Nonmetals– Electron acceptors– Accept valence electrons to become a

negative ion (anion)

Ionic Bonding

Ionic Bonding

The oppositely charged ions are attracted to each other by a

force called an ionic bond

• Most ionic compounds:• Have high melting points• Are hard and brittle• Are soluble in water• Form electrolytes (conduct electricity)

when dissolved in water

Properties of Ionic Compound

Crystal Lattice Structure• Ionic compounds form crystal

lattices• This explains why they have

high melting points and are hard but brittle

Na+ Cl-

Ionic Compounds in Water

When ionic compounds dissolve, they separate into their ions

The free ions can now move and conduct electricity

Naming Ionic Compounds• Many ionic compounds are made up of a

metal and a nonmetal• The metal is named first, followed by the

nonmetal• Change the nonmetal ending to “ide”

E.g. aluminum and oxygen = aluminum oxide magnesium and chlorine = magnesium chloride

Do NOT capitalize

Common Anions NameH- hydrideF- fluorideCl- chlorideBr- bromideI- iodide

O2- oxideS2- sulfideN3- nitrideP3- phosphide

Writing the Chemical Formula

• Step 1: Write the symbols of the elements, with the metal on the left-hand side and the non-metal on the right-hand side.

Mg Cl• Step 2: Add the ionic charge of each ion

above the symbol+2 -1Mg Cl

• Step 3: Determine the number of ions required to bring the charge to zero.

1(+2) + 2(-1) = 0 Mg Cl

• Step 4: Write the chemical formula using the (red) coefficients in front of each bracket as subscripts

Mg1Cl2 Note: Do not write the subscript “1”

The chemical formula for magnesium chloride is MgCl2

Crisscross Method

• Step 1: Write the symbols of the elements and their ionic chargesMg 2+ Cl-

• Step 2: Crisscross the numbers of the ionic charges so that they now become subscripts Mg 2+ Cl-

MgCl2

Multivalent Metals• Some metals have multiple ionic charges.E.g. Write the chemical name of CuBr2. • Copper could have either +1 or +2 • Each bromide ion has a charge of -1, so the total

charge of bromide ions is 2(-1).• The ionic charge of copper in this compound is +2• Roman numerals are included ONLY if the metal

has more than one ionic charge.• The name of CuBr2 is copper (II) bromide

Practice!