Ionic Compounds and Metals

Types of bonds A chemical bond is the force that holds atoms together in a molecule. Ionic bonds form when electrons are transferred between atoms. Covalent bonds form when electrons are shared between atoms.

Electronegativity Electronegativity is a measure of the attraction a bonded atom has for electrons. Electronegativity increases from bottom to top and from left to right.

Formation of Ionic Bonds If the electronegativity difference is large (a metal with a nonmetal) an ionic bond will form. Ionic bonds are the strongest type of bond. Substances resulting from ionic bonds are classified as crystalline solids.

Let’s Practice Identify the type of bond (ionic or covalent) that will form between each pair of atoms. Na and Cl C and O N and H Ca and O K and N Mg and F

Example

Forming Ions When neutral atoms gain or lose valence e- an ion is formed. Ions are atoms with a charge Cations have a positive charge (K+, Li+) Anions have a negative charge (F-, I-)

Ions forming bonds Cations are attracted to anions because of opposite charges. “Opposites attract”

Why do ions form? Ions form to attain a more stable electron configuration. Remember that a Noble gas configuration is the most stable Ne - ___ ___ ___ ___ ___ 1s 2s 2p All Noble Gases have a full octet (8 valence e-)

Noble Gases

Why do ions form? Na __ __ __ __ __ __ 1s 2s 2p 3s Now Na+ looks like neon Ne __ __ __ __ __ 1s 2s 2p All atoms are trying to have a Noble Gas electron configuration so, they will lose or gain electrons to get there

Why do ions form? F __ __ __ __ __ 1s 2s 2p F- __ __ __ __ __ 1s 2s 2p Ne __ __ __ __ __

Review Draw the dot notation for each element and the charge of its ion N S Ba Li

Ionic Bonds Ionic bonds- the force that holds two oppositely (+ and -) charged particles together. Ionic compounds contain ionic bonds and are neutral Usually forms between a metal and a nonmetal

Forming Ionic Bonds

Forming Ionic Compounds Write an equation showing how ionic compounds are formed for the following elements. Na and I Mg and O Al and Cl

Properties of Ionic Compounds Shape The Ionic bond produces unique characteristics for ionic compounds Crystals are created by repeating patterns of cations and anions. This balances the forces between the ions. This is called a crystal lattice

Properties of Ionic Compounds Physical Properties Electrolytes (aqueous ions- Ions dissolved in water) conduct electricity Solid ionic compounds DO NOT conduct electricity because the charges are locked in place

Properties of Ionic Compounds Physical Properties Ionic solids are strong and hard to break apart High Melting points High Boiling points Transition metals in the crystal give the ionic solid color.

Properties of Ionic Compounds Physical Properties The solid ionic crystals are hard, rigid, and brittle The strong forces between ions produce this property

Ionic Compounds Ionic compounds are repeating patterns of the cation and anion. The simplest ratio of ions involved is called a formula unit. NaCl is the formula unit for table salt

Ions in Ionic Compounds Monatomic ions- ions made of only one type of atom (Cl-, F-, Li+) Polyatomic ions- ions made of at least two different types of ions (OH-, NH4+) Cation + Anion  Ionic Compound

Writing formulas for ionic compounds Binary ionic compounds contain a single cation and anion. Remember that the final compound must be neutral so the charges must balance. Ca+2 Cl-  CaCl2

Cris-Cross method Record the ion symbol and charge The # of the charge of the cation becomes the subscript for the anion and the # of the charge for the anion becomes the subscript for the cation. The #1 does not have to be recorded it is understood. Al+3 O-2  Al2O3

Cris-Cross method Al2O3 is the formula units for aluminum oxide. The subscripts indicate how many ions are needed of each in order to balance the charges.

Try a few Potassium and Iodide Magnesium and chloride Aluminum and bromide Cesium and nitride

Naming Ionic Compounds NaBr Name the cation then the anion. Cations are always written first Monatomic cations always keep their name. If the cation is an ion that may carry multiple charges then a roman numeral is used to indicate which charge the cation is carrying. [Fe+3 (III) and Fe+2 (II)].

Naming Ionic Compounds The monatomic anion’s ending is changed to -ide. Fluorine is changed to Fluoride. NaBr- sodium bromide Fe3N2 – Iron (II) nitride

Let’s practice CaCl2 K2O CuCl2 Fe2O3

What about Polyatomic ions? Al+3 and PO4-3  AlPO4 The same rules apply, however NEVER CHANGE A SUBSCRIPT THAT IS ALREADY THERE. Polyatomic ions may also require () around them if there is a need for more than one to balance the charge