An Introduction to Ionic Bonding Unit XX, Presentation 1.

An Introduction to Ionic Bonding

Unit XX, Presentation 1

Keeping Track of Electrons The electrons responsible for the chemical

properties of atoms are those in the outer energy level.

Valence electrons - The s and p electrons in the outer energy level.– Dealing with transition metals is a bit more

complex, but we still mostly deal with s and p electrons first

Core electrons -those in the energy levels below.

Keeping Track of Electrons Atoms in the same column

– Have the same general outer electron configuration.

– Have the same valence electrons. Electrons can easily be found by

looking up the group number on the periodic table.– Group 2 - Be, Mg, Ca, etc.-– 2 valence electrons

Electron Dot diagrams A way of keeping track of

valence electrons. How to write them

– Write the symbol.

– Put one dot for each valence electron

• Don’t pair electrons up until there are no open spots left

X

The Electron Dot diagram for Nitrogen

Nitrogen has 5 valence electrons.

First we write the symbol.

NThen add 1 electron at a time to each side.Until they are forced to pair up.

Write the electron dot diagram for

Na Mg C O F Ne He

Electron Configurations for Cations

Metals lose electrons to attain noble gas configuration.

They make positive ions. If we look at electron configuration it

makes sense. Na 1s22s22p63s1 - 1 valence electron Na+ 1s22s22p6 -noble gas configuration

Electron Dots For Cations Metals will have few valence electrons

Ca

Electron Dots For Cations Metals will have few valence electrons These will come off

Ca

Electron Dots For Cations Metals will have few valence electrons These will come off Forming positive ions

Ca+2

Electron Configurations for Anions

Nonmetals gain electrons to attain noble gas configuration.

They make negative ions. If we look at electron configuration it

makes sense. S 1s22s22p63s23p4 - 6 valence electrons S-2 1s22s22p63s23p6 -noble gas

configuration.

Electron Dots For Anions Nonmetals will have many valence

electrons.

P

Electron Dots For Anions Nonmetals will have many valence

electrons. They will gain electrons to fill outer shell.

P

Electron Dots For Anions Nonmetals will have many valence electrons. They will gain electrons to fill outer shell. Forming negative ions

P -3

Stable Electron Configurations All atoms react to achieve noble gas

configuration. Noble gases have 2 s and 6 p electrons.

– Again, we ignore the d electrons– 8 valence electrons .

This is called the octet rule.

Ar

Stable Electron Configurations Which elements on the periodic table do

not achieve a true octet when making stable, naturally occurring ions?

H+1, Li+1, Be+2, B+3, H-1

Ionic Bonding Anions and cations are held together by

opposite charges.

– Attraction between opposite charges is called electrostatics

Ionic compounds are called salts.

– Salts are what is left over when an acid and base react

Ionic Bonding The simplest ratio of the atoms in an ionic

compound is called the formula unit.

Ionic bonds are formed through the transfer of electrons.

Electrons are transferred to achieve noble gas configuration for both atoms/ions.

Ionic Bonding

Na Cl

Ionic Bonding

Na ClElectronegativity applies here.

The chlorine has a higher attraction to the electrons so . . .

Ionic Bonding

Na Cl

The electron is transferred to the chlorine

Ionic Bonding

Na Cl

The electron is transferred to the chlorine

Ionic Bonding

Na+ Cl-

Making the atoms into ions

Ionic Bonding

Na+ Cl-

Ionic Bonding

Na+ Cl-

Ionic Bonding All the electrons must be accounted for!

Ca P

Ionic Bonding

Ca P

Ionic Bonding

Ca+2 P

Ionic Bonding

Ca+2 P

Ca

Ionic Bonding

Ca+2 P-3

Ca

Ionic Bonding

Ca+2 P-3

Ca P

Ionic Bonding

Ca+2 P-3

Ca+2 P

Ionic Bonding

Ca+2 P-3

Ca+2 P

Ca

Ionic Bonding

Ca+2 P-3

Ca+2 P

Ca

Ionic Bonding

Ca+2 P-3

Ca+2P

-3

Ca+2

Ionic Bonding

Ca3P2

Formula Unit