IONIC AND METALLIC BONDING

CH 7

I. Valence Electrons

Electrons in the highest occupied energy level of an element’s atoms

To find the number of valence electrons in an atom of a representative element, simply look at its group number. If it’s in group 1 or 2. If it is in groups 13-18 subtract 10 to find the number of valence electrons.

II. Octet Rule

In the formation of compounds, atoms tend to achieve the electron configuration of a noble gas.

Atoms either gain, lose, or share electrons to form compounds.

III. Cations

Loses an e-

-An atom’s loss of valence electrons produces a cation, or a positively charged ion.

III. Cations Metals – lose valence e- easily Transition metals – have 2 valence e-, usually

lose those two to form 2+ ions, but can also lose d electrons to form other ions

IV. Anions

Nonmetals easily gain e- to form negative ions to get to 8 valence e-

Gains an e-

Chloride ion

IV. Anions

-Nonmetals usually gain e- Some can gain or lose, but will gain most often

Formula Unit-The lowest whole-number ratio of ions in an ionic compound.

V. Ionic Bonds

When oppositely charged ions attract, electrostatic force that holds them together = ionic bond

Compounds containing ionic bonds = ionic compounds

Electrons are transferred from cations to anions

Bonds formed between metals and nonmetals (or contain a polyatomic ion)

V. Ionic Bonds

Na·

1s2 2s2 2p6 3s1 1s2 2s2 2p6 3s2 3p5

RESULTS IN

Na+

1s2 2s2 2p6 1s2 2s2 2p6 3s2 3p6

VI. Properties of Ionic Compounds

Most ionic compounds are crystalline solids at room temperature. Arranged in repeating three-dimensional

patterns Ionic compounds generally have high

melting points Large attractive forces result in very stable

structures

VI. Properties of Ionic Compounds

Ionic compounds can conduct an electric current when melted or dissolved in water. When ionic compounds are dissolved in water

the crystalline structure breaks down. This allows the ions to move freely which results in conductivity.

The positive Na ions move to the cathode and the negative Cl ions move to the anode.

VII. Metallic Properties

Metals are good conductors because the valence electrons are able to flow freely within them. Valence electrons of metals can be thought of

as a sea of electrons.

VII. Metallic Properties

The ductility and malleability of metals can be explained by the mobility of electrons in metals. When a metal is subjected to pressure , the

cations easily slide past each other like a ball bearing immersed in oil. If an ionic crystal is stuck with a hammer the cations are pushed together, repel, and the crystal shatters.