Ch. 6 Bonding 6.3 Ionic Bonding

Ionic Compounds ionic bonds do NOT form molecules ionic bonds do NOT form molecules chemical formulas for ionic compounds represent the simplest ratio of ion types chemical formulas for ionic compounds represent the simplest ratio of ion types made of anions and cations made of anions and cations

Ionic Compounds combined so that positive charges balance negative charges combined so that positive charges balance negative charges crystalline solid crystalline solid formula of ionic compound depends of the charges of the ions combined formula of ionic compound depends of the charges of the ions combined

Binary Ionic Compounds Because positive charges must balance negative charges, use criss-cross method to make formulas. Write the formula for aluminum oxide. Because positive charges must balance negative charges, use criss-cross method to make formulas. Write the formula for aluminum oxide.

Binary Ionic Compounds If you don’t like criss-cross, use algebra. Write the formula for barium sulfide.

Formation attractive forces: attractive forces: oppositely charged ions (main attraction)oppositely charged ions (main attraction) nuclei and electron clouds of adjacent ionsnuclei and electron clouds of adjacent ions repulsive forces: repulsive forces: like-charged ions (main repulsion)like-charged ions (main repulsion) electrons of adjacent ionselectrons of adjacent ions

Formation distance between the ions creates a balance between those forces distance between the ions creates a balance between those forces ions minimize their PE by combining in an orderly arrangement called a crystal lattice ions minimize their PE by combining in an orderly arrangement called a crystal lattice

Formation Specific lattice pattern created depends on: charges of ions charges of ions determines number of electrons transferreddetermines number of electrons transferred determines the ratio of ionsdetermines the ratio of ions size of ions size of ions larger ions need more spacelarger ions need more space

Lattice Energy energy released when separate gaseous ions bond to form ionic solid or the energy absorbed to break the bonds between ions energy released when separate gaseous ions bond to form ionic solid or the energy absorbed to break the bonds between ions the larger the amount of energy, the stronger the bond the larger the amount of energy, the stronger the bond more electrons transferred or smaller ions leads to a larger lattice energy more electrons transferred or smaller ions leads to a larger lattice energyNaCl-787.5NaBr CaF CaO-3385 LiCl MgO-3760 KCl-715

In each of the following pairs of compounds, identify the one with the higher lattice energy KCl, CaS KCl, CaS LiF, NaCl LiF, NaCl Fe 2 O 3, MnO 2 Fe 2 O 3, MnO 2 CaO, CaCl 2 CaO, CaCl 2