How charged atoms come together to make compounds 5.6 & 5.7 Ionic Compounds How charged atoms come together to make compounds

RECALL Non-metals gain electrons and become negatively charged anions Metals lose electrons and become positively charged cations Atoms lose or gain electrons in order to achieve a full valence orbit of electrons

Opposites Attract Elements combine in specific ratios to balance their charges. Must have a net charge = 0 IONIC COMPOUNDS -Compounds that are made of positive and negative ions IONIC BOND - attraction that holds oppositely charged ions together in a compound

Example 1 NaCl Na  metal, loses one electron Charge is +1 Cl  non-metal, gains one electron Charge is -1 Na+ and Cl- makes NaCl

Example 2 What is the formula for the ionic compound formed by calcium and iodine? Step 1) Determine the number of valence electrons , and charge on each atom Iodine is found in column 17, so we know it has Ca a charge of 1- Calcium has a charge of 2+ Iodine has a charge of 1- 2 8 8 2

Example 2 cont’d Step 2: Write the elements side by side with charges on top: Ca2+ + I1- Step 3: Cross the charges to determine the amount of each atom in the compound: Step 4: write the final compound CaI2

Example 3 Write the formula for the ionic compound formed between Sodium and Oxygen Step 1/2: Determine the charges on Na and O and write above: Na1+ + O 2- Step 3 : Cross the charges Step 4: Write the final ionic compound Na2O

Example 4 Write the formula for the ionic compound formed between Aluminum and Sulfur Step 1/2: Determine the charges on Al and S and write above: Al3+ + S 2- Step 3 : Cross the charges Step 4: Write the final ionic compound Al2S3

Tricks to Formulas Write symbols (with metal first) Write ionic charges above the symbol (from periodic table) Balance the number of each atom needed to reach a total charge of 0 (criss cross) Write formula with subscripts (small numbers following the atomic symbols)

Naming Ionic Compounds Metal name is the same as it is on the periodic table Non-metal name has the ending after the stem changed to “ide” Examples NaCl  Na2O  CaBr2

Tricks to naming Metal ALWAYS comes first It doesn’t matter how many of each atom you have the name does not change Examples AlN Al2S3