Ch. 7 Ionic and Metallic Bonding

7.1 Ions

I. Valence Electrons• A. # of electrons in highest occupied S and P orbitals• B. Based on P.T. location• C. Only valence electrons used in bonding

1 2 3 4 5 6 7 8Valence electrons

II. Electron Dot Models• A. Write valence electrons as dots around

atomic symbol (maximum 2 e- per side)

• B. Ex. Carbon (4 valence electrons)

Try These:

Sodium (Na) Fluorine (F) Aluminum (Al)

III. Octet Rule• A. Having 8 valence e- is the most stable

• B. Atoms lose or gain e- to have an octet

• C. Become charged (ions); + cations, - anionsValence: 1 2 3 4 5 6 7 8

Lose or Gain: 1 2 3 3 2 1 0

Charge: +1 +2 +3 -3 -2 -1 0

IV. Why Form an Ion?• A. Cation Example: Magnesium (12e-)

– Mg atom : 1s2 2s2 2p6 3s2 (loses 2e-)– Mg2+ ion : 1s2 2s2 2p6

• B. Anion Example: Oxygen (8e-)–O atom : 1s2 2s2 2p4 (gains 2e-)–O2- ion : 1s2 2s2 2p6

Octet

Octet

V. Transition Metals• A. Can form pseudo-noble gas configurations

• B. Ex. CopperCu (29 e-) 1s2 2s2 2p6 3s2 3p6 4s2 3d9 is what you

would expect

Actual config: 1s2 2s2 2p6 3s2 3p6 4s1 3d10 (because full D more stable than full S)

Lose 1 e- from 4s: 1s2 2s2 2p6 3s2 3p6 ___ 3d10 (Cu+)

Pseudo-Noble gas Configuration

7.2 Ionic Bonds and Ionic Compounds

I. Formation• A. Ionic Bonds: electrostatic attractions

between oppositely charged ions

• B. Ionic compounds neutral, opposite charges cancel

• C. Example: Sodium (Na) and Chlorine (Cl)

•D. Na+ and Cl- will form ionic bonds to become NaCl

II. Using Electron Dot Models• A. Electron dot models can show ionic bonding• B. Example: Sodium (Na) and Oxygen (O)

III. Properties• A. Most ionic compounds form crystals in solid state• B. Formula unit: lowest ratio of cations to anions

• C. Strong bonds, cause high melting temperatures

7.3 Metallic Bonds

I. Metallic Bonds Properties• A. Attraction between valence electrons and

positively charged metal ions• B. free floating valence electrons (“sea of electrons” allow metals to be molded (malleability)

II. Metal Crystals• A. Body-centered cubic: metal in middle

of cube and at each corner• B. Face-centered cubic: in center of each side and at corners• C. Hexagonal close-packed: metals in

hexagon shape with three in middle

III. Alloys• A. Mixture of a metal and other elements• B. Ex. Brass = Copper and Zinc• C. Better properties than their parts• D. Elements can replace metals (substitutional)

or be incorporated into the spaces between them (interstitial)

Substitutional Alloy Interstitial Alloy