Chapter 15 Ionic Bonding and Ionic Compounds

What is an Ionic Bond?

Ionic Bond l Bond formed between a metal and nonmetal.

Why do atoms bond? l Atoms bond in order to acquire a full set of valence electrons. l Most of the time this is 8. This is known as the octet rule. l Atoms will gain, lose or share in order to attain a full set of electrons

Valence Electrons l The electrons responsible for the chemical properties of atoms are those in the outer energy level. These electrons are called the valence electrons. l Valence electrons - The electrons in the outer energy level

Electron Configuration

Electron Configuration… Maybe you learned it this way

Electron Configurations for Cations l Metals lose electrons to attain noble gas configuration. l They make positive ions (cations) l If we look at the electron configuration, it makes sense to lose electrons: l Na 1s 2 2s 2 2p 6 3s 1 1 valence electron l Na 1+ 1s 2 2s 2 2p 6 noble gas configuration

Electron Configurations for Anions l Nonmetals lose electrons to attain noble gas configuration. l They make negative ions (anions) l If we look at the electron configuration, it makes sense to lose electrons: l F 1s 2 2s 2 2p 5 2 valence electrons l F -1 1s 2 2s 2 2p 6 noble gas configuration

Keeping Track of Electrons l Atoms in the same column... –Have the same valence electrons. l LABEL!

Bohr Model of the Atom The Bohr Model has an atom consisting of a small, positively-charged nucleus orbited by negatively-charged electrons.Bohr Model 1 st shell: 2 electrons 2 nd shell: 8 electrons 3 rd shell: 18 electrons

Example: Bohr Model of Nitrogen

CHEM-IS-TRY Draw the Bohr Model of Fluorine

Electron Dot diagrams l A way of keeping track of valence electrons. l How to write them? l Write the symbol. l Put one dot for each valence electron l Don’t pair up until they have to (Hund’s rule) X

The Electron Dot diagram for Nitrogen l Nitrogen has 5 valence electrons. l First we write the symbol. N l Then add 1 electron at a time to each side. l Until they are forced to pair up.

Write electron dot diagrams: l Na l Mg lClC lOlO

Properties of Ionic Compounds l A regular repeating arrangement of ions in the solid: this is known as a lattice. Structure is rigid. l High melting points

Crystalline structure

Do they Conduct? l Conducting electricity is allowing charges to move. l In a solid, the ions are locked in place. l Ionic solids are insulators. l When melted, the ions can move around. Therefore, they have the ability to conduct electricity l Ionic Compounds dissolved in water conduct

Completing the Circuit