Atoms and Bonding Notes

 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).

 Valence electrons are represented on atoms in Lewis dot structure, which show unpaired electrons and paired electrons

 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:  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  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, valent- valence electrons) bond and the compound of water is a covalent compound.