an introduction to ionic bonding unit xx, presentation 1
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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.
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 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. 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 ClElectronegativity applies here.
The chlorine has a higher attraction to the electrons so . . .
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