Three Types Of Bonding Chemical Bonding Sheet
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1
2There are three general classes of bonds that form between
atoms. You can predict which will form by classifying the
atoms as metals or nonmetals:
metal + metal
metallic bond
Au-Ag alloy
15 • Chemical Bonding
metal + nonmetal
ionic bond
MgCl
2
Three Types of Bonding
nonmetal + nonmetal
covalent bond
SO
or CH
2
4
(1 of 8)
Some compounds can contain both ionic and covalent
bonds such as K
SO
... the sulfate ion is held together with
2
4
covalent bonds... the potassium ions are ionically bonded to
the sulfate ions.
Acids are exceptions... they are ionic only when dissolved.
Many ions can be explained because they have gained or lost
electrons and attain a noble gas configuration.
3–
2–
–
+
2+
For example:
P
S
Cl
Ar K
Ca
2
2
6
2
6
all have the same electron arrangement: 1s
2s
2p
3s
3p
15 • Chemical Bonding
The importance of this configuration is that this is one
The Ionic Bond
reason why ions form. After these ions form, they stick
(2 of 8)
together in a crystal lattice because opposites attract:
+ - + - + - + -
- + - + - + - + There are other reasons why some
+
2+
+ - + - + - + - ions (ex: Cu
or Zn
) form. One is
- + - + - + - + the pseudonoble gas configuration.
+ - + - + - + -
The covalent bond between two atoms depends on the
balance of attractions between one atom’s + nucleus and
the other atom’s – electrons and the proton-proton
repulsions as well as electron-electron repulstions.
15 • Chemical Bonding
The Covalent Bond
PE
(3 of 8)
Distance between nuclei
If two atoms have half-filled orbitals, the interactions
–
balance at a small enough distance so the e
’s can be close
to both nuclei at the same time... this is a covalent bond.
Count up your valence electrons.
Give every atom who “wants” and octet an octet.
[the first 5 elements do not need octets... too small]
[Family I, II, and III do not form octets]
15 • Chemical Bonding
Groves’ Electron Dot System
If you have drawn too many electrons... ex: C
H
2
2
Multiple & Extended Valence Bonds
“Take away a lone pair... take away a lone pair...
make these two atoms share”
(4 of 8)
If you have drawn too few electrons... ex: PCl
5
Place the extra electrons on the central atom (extended
valence shell)
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