Atoms and Bonding Notes
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Recall every atom of an element has neutrons and protons in their nucleus and
have electrons circling around the nucleus.
Electrons are found in different levels called “shells”
→Electrons in the outermost shell of any atom give that atom its chemical properties,
including its ability to form chemical bonds.
→These electrons are valence electrons and the fill the valence shell (outermost shell).
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Valence electrons are represented on atoms in Lewis dot structure, which show
unpaired electrons and paired electrons
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ONLY the unpaired electrons can form bonds
►Atoms lose or gain electrons so they can end up with an outermost occupied shell filled
to capacity (and all of the electrons paired).
→This is called the octet rule because the outermost shell is occupied when it has
EIGHT electrons. The only atoms that follow the octet rule by themselves are the
noble gases (Neon, Argon, Krypton, etc).
Two types of Bonds:
 Result from interactions with unpaired valence electrons.
Ionic:
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Transfer of valence electrons
Common example: NaCl
Sodium (Na) wants to lose one electron to achieve octet rule
Chlorine (Cl) wants to gain one electron to achieve octet rule
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The transfer of one electron from Na to Cl causes them to electrically have
opposite charges and thus be pulled toward each other
This electric force of attraction is an ionic bond and the compound of table salt is
an ionic compound.
Covalent:
 Sharing of electrons
 NEITHER atom gets full possession of the unpaired electron
 BUT both considered in possession of the electron because they both are using the
electron to fill their valence shell
 Examples include H2O and most diatomic elements like O2, F2 and N2
 This mutual attraction for shared electrons creates a covalent (co-sharing, valentvalence electrons) bond and the compound of water is a covalent compound.