Ionic Bonds

Review!

• Ion – atom that is no longer neutral because it has lost or gained electrons Now it has an electric charge!

• Atoms with 5, 6 or 7 valence e- become more stable when that number increases to 8.

• Atoms with 1, 2 or 3 valence electrons can become more stable when they lose electrons.

Lose e- become positive ionGain e- become negative ion

Ions and Their ChargesIons and Their Charges

Name Charge Symbol or Fomula

Lithium 1+ Li+

Sodium 1+ Na+

Potassium 1+ K+

Ammonium 1+ NH4+

Calcium 2+ Ca2+

Magnesium 2+ Mg2+

Aluminum 3+ Al3+

Fluoride 1- F-

Chloride 1- CL-

Iodide 1- I-

Bicarbonate 1- HCO3-

Nitrate 1- NO3-

Oxide 2- O2-

Fsulfide 2- S2-

Carbonate 2- CO32-

Sulfate 2- SO42-

Phosphate 3- PO43-

What does this chart mean?!

• How does Li have a +1 charge?

• How does Aluminum have a +3 charge?

• Notice how the names of F, Cl, and I have changed? Why?

Polyatomic Ions

• Polyatomic Ions – Ions that are made of more than one atom.– Ammonium– Bicarbonate• Group of atoms that reacts as a unit

– Have overall positive or negative charge

Ionic Bonds• The attraction between

two oppositely charged ions– Form as a result of

positive and negative ions being attracted to each other.

• Form ionic compounds!• Usually form between a

metal and nonmetal!

• When ionic compounds form, ions bond in a way that balances out the charges on the ions.

• The chemical formula for the compound reflects this balance.– combination of symbols that shows the

ratio of elements in a compound

Formulas of Ionic Compounds

Subscript - tells you the ratio of elements in the compound• if no subscript – it’s understood to be

1

Naming Ionic Compounds

• The name of the (+) ion comes first, followed by the name of the (-) ion. – Positive ion is usually a metal.

• If the negative ion is a single element,end of it’s name changes to –ide.• NaCl Sodium Chloride• MgO Magnesium Oxide

• If the negative ion is polyatomic:– Ends with -ate or -ite• NH4NO3 ammonium nitrate (fertilizer)

Ionic Crystals

• Form solids by building up repeating patterns of ions.– Have orderly, three dimensional

arrangement called a crystal.– Every ion is attracted to ions of opposite

charge that surround it.–Many crystals are hard and brittle, due

to the strength of their ionic bonds

High Melting Points• When ions have enough energy to

overcome the attractive forces between them, they break away from each other.– Crystal melts into liquid– A lot of energy is needed to break these

bonds

Electrical Conductivity

• When ionic crystals dissolve in water, the bonds between ions are broken.

• Ions are free to move about & the solution conducts current.

• Solids do not conduct current well good insulators