Chemical Bonding: Ch. 7: Ionic Bonding

Chapter 7: Ionic Bonding First off – what you need to remember before getting into this chapter…

The cool kids… Every element wants to be like the noble gases. This will be important this chapter.

What is an Ion? An atom that has lost or gained electrons to become positively or negatively charged. Write an example:

Using the periodic table for ion information. Prediction of charges: Alkali metals (Group 1A)= +1 Alkaline earth metals (Group 2A) = +2 Oxygen family (Group 6A) = -2 Halogens (Group 7A)= -1 Noble gases (Group 8A) = 0

Valence Electrons Elements in the same group have similar properties because they have the same number of valence electrons. The electrons in the highest occupied energy orbital When chemicals combine we look at…

How do I find valence electrons? The number of valence electrons = the group number of the element on the periodic table. The exceptions – noble gases: He has 2 valence e-, the rest have 8.

How many valence electrons? A) C B) Cl C) Ca D) As E) Xe F) Cs G) Al

Valence electrons are usually the only electrons that take part in a chemical bonds. and… Chemists like to draw pictures.

Electron Dot Structures Represent each electron as a dot Sodium has 1 valence electron: We don’t care where the first dot is, just that there is one dot.

Adding the next dots.. Add 2 nd dot to a different side of the element. Be C B

The fifth dot… When there are no more empty sides, add a second dot (no more than 2 dots per side)

The cool kids… Every element wants to be like the noble gases. This will be important this chapter.

The Octet Rule Noble gases = unreactive because they have 8 outer electrons Atoms lose, gain, or share electrons to get 8 electrons in the outer shell

Ionic Compounds To be stable (a happy atom), atoms completely gain or lose an electron (no sharing)

Examples: Mg Ca Al

Anions work the same way… It is easier for some atoms to gain electrons to obtain the octet. Ex) S Ex) Br

So this is why I gave you these charges last chapter… Prediction of charges: Alkali metals = +1 Alkaline earth metals = +2 Oxygen family = -2 Halogens = -1 Noble gases = 0

Ionic Bonding Metal + nonmetal Cation + anion Positive + Negative Example: NaCl

Ionic Compounds Electrically Neutral (…charges balance ALWAYS) Properties High melting point Solids at room temperature When melted and dissolved, conduct electricity

Ionic Bonds Ionic Bonds: Electrostatic forces that hold ions together Positives and Negatives are attracted to each other (like magnets)

Where do these electrons go/come from? NaCl Forms an ionic bond

Electron Configurations and Ionic Bonding Sodium Chloride Example

Predicting the formula Mg and Cl K and S Ca and S Al and O Al and F