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Intro to Ionic/Covalent Video
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What is the “goal” of atoms? What makes them
happy?
To achieve a filled valence shell.
To do this, atoms must gain or lose electrons to
form ions. Others share electrons.
Ion- an atom that has gained or lost an
electron, and therefore has a positive or
negative charge based on the number of
electrons it has lost.
Electronegativity is a measure of the tendency of
an atom to attract a bonding pair of electrons.
(How much an atom wants to gain an electron)
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If the difference in
electronegativities is between:

1.7 to 4.0: Ionic

0.3 to 1.7: Polar Covalent

0.0 to 0.3: Non-Polar Covalent
Example: NaCl
Na = 0.8, Cl = 3.0
Difference is 2.2, so
this is an ionic bond!

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Cation- positively charged ion (loses e-)
Anion- negatively charge ion (gains e-)
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Ionic Bondcomplete transfer
of 1 or more
electrons from one
atom to another
(one loses, the
other gains)
forming oppositely
charged ions that
attract one
another
Good Animation on
Ionic Bonding

Covalent Bondsome valence
electrons are
shared between
atoms to
achieve a “full”
valence shell.
A bond can result from an overlap of
atomic orbitals on neighboring
atoms.
••
H
+
Cl
••
•
•
H
••
Cl
••
Overlap of H (1s) and Cl (3p)
Note that each atom has a single,
unpaired electron.
•
•
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Remember that valence
electrons are the electrons in
the OUTERMOST energy
level… that’s why we did all
those electron configurations!
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2 Methods:

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Draw up the Lewis Dot Structures.
Swap Charges (works only for ionic)
How to Make Ionic Bonds

Step 1, determine the # of valence
electrons (either through group #
for first 18 or through looking at
electron configuration)
If you can lose them, then you get a +
charge. Why?
 If you need them, you get a (-) charge.
Why?

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Step 2, Then write the Atomic
Symbol, surrounded by the
electrons represented as dots.
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Step 3, place the dot structures next to each
other (cation first if ionic bond). Then exchange
dots.
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Write each of the atoms with their charges.
Then swap the charges down to the front of the
other atom to determine how many you need
of each to balance out the charges.
Ex: Mg 2+ and Cl – make: MgCl2