The Octet Rule Ionic BondingIonic BondingIonic BondingIonic Bonding

• Noble gases are unlike any other group of elements on the periodic table because of their extreme stability ( they don’t want to interact with other elements)

• Each noble gas has eight valence electrons, except for helium, which has two.

• The octet rule says that atoms can become stable by having eight electrons in their outer energy level.

Example

• Sodium is in Group 1, so it has 1 valence electron.

• Chlorine is in Group 7A and has 7

valence electrons.

What will happen if the two want to combine?

Ionic bonding

• How can the valence electrons of atoms rearrange to give each atom a stable configuration of valence electrons?

• If the one valence electron of sodium is transferred to the chlorine atom, chlorine becomes stable with an octet of electrons

Electrons Can Be Transferred

• Because the chlorine atom now has an extra electron, it has a negative charge.

• Also, because sodium lost an electron, it now has an unbalanced proton in the nucleus and therefore has a positive charge.

• Now that each atom has an octet of outer-level electrons, they are no longer neutral atoms; they are charged particles called ions.

• An ion is an atom or group of combined atoms that has a charge because of the loss or gain of electrons.

• A compound that is composed of ions is called an ionic compound.

Ionic Ionic BondingBonding

Ionic compounds, like table salt: NaCl, usually form crystals of repeating ion pairs by combining a metal with a nonmetal element.

Ex: KI, CaCl2, BaF2, NaCl, Li2O, Al2S3

Ionic bonding

• NACL crystals form repeating patterns of positive and negative ions to maximize the distance between like charges

• When ionic compounds melt or dissolve in water, their three-dimensional structure breaks apart, and the ions are released from the structure.

Covalent bonding

• Now what if the following atoms want to combine?

• Cl-Cl

• N-N

• O-O

• C-O

Covalent bonding

• If two chlorine atoms combine, they share a single pair of electrons, and each atom attains a stable octet configuration.

Covalent bonding

• Two oxygen atoms share two pairs of electrons to form O2, and two nitrogen atoms share three pairs of electrons to form N2.

Electron Sharing Produces Molecules

• Notice that in a covalent bond, atoms share electrons and neither atom has an ionic charge.

• The attraction of two atoms for a shared pair of electrons is called a covalent bond.

Covalent Bonds:Sharing of pairs of valence electrons

between nonmetals.