Chapter 6 Section 3 Ionic Bonding and Ionic Compounds

Remember these things?? Ion is a charged particle Cation is a positive particle Anion is a negative particle Opposites attract Ionic compound is one that is made up of ions.

Ionic compounds Are crystalline solids This means the atoms are arranged in a regular repeating pattern The compound is 3-D Not made of independent units Formulas show the simples ratio of ions in the compounds

Formula Unit Simples ratio of atoms in an ionic compound Shows the number of positives to the number of negatives We will learn how to name and write formulas for these in chapter 7

Formation of Ionic Compounds Electron dot notation is good to understand how this happens Important things to remember to make this easier Metals loose electrons Metals loose valence electrons to become like Noble Gasses Become positive ions--cations Non-metals gain enough electrons to become like Noble Gasses Become negative ions--anions

Illustration of ionic bond formation Note how the one valance electron from Na transfers to Cl. This gives both atoms an octet of electrons.2p205scienceeportfolio. From wikispaces.com

Characteristics of Ionic Bonding Nature favors low potential energy Ionic crystals minimize this energy Crystal lattice is an orderly arrangement that makes this minimization happen Forces between like charges balance with forces between unlike charges

Pictures of ionic crystals Picture of soduim chloride crystals lattice from chemistry.wustl.edu. Notice that the center Na is surrounded by 8 Cl. Notice how each + is surrounded by -. Picture from bbc.co.uk

Energy To look at bond strength must look at energy released when the ions join Called lattice energy Definition energy released when one mole of an ionic crystalline compound is formed from gaseous ions

Bond Strength Forces between ions is strong Bond strength affects the properties of the solids

Characteristics of ionic compounds High melting point High boiling point Brittle Hard Conduct electricity when melted or dissolved in water Dissolve in water Ions separated when put in water

Characteristics of covalent compounds Low melting point So low many are gases at room temperature Malleable Do not conduct electricity Some will dissolve in water Most are insoluble in water

Polyatomic Ions Covalently bonded group of atoms Has molecular characteristics Has ionic characteristics Polyatomic ions Charge (ion) Group (poly) of atoms Covalently bonded to each other

Polyatomic ions continued Can be positive or negative Will be positive if the total protons outnumber the total electrons Will be negative if the total electrons out number the total protons Lewis structures can be drawn in the same manner as before We will spend LOTS of time with these in the next chapter

Pictures of Lewis Structures for polyatomic ions This is ammonia’s Lewis diagram. Notice the overall positive charge. Image from shodor.org This is the phosphate ion’s Lewis diagram. Notice how each atom has 8 electrons around it. Image from 800mainstreet.com