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Interest Grabber

Observing Charged ObjectsRecord your observations as your teacher does the following demonstration. Cut two pieces of string about 3 feet in length (or long enough to extend from your teacher’s head to the ceiling). Tie the ends of the strings together and use a thumbtack to hang them from the ceiling. Tie a balloon to the end of each string. Stand under and between the balloons and rub both them on your hair. Let go of the balloons and walk away from them.

1. What happens to the balloons?

2. Offer an explanation for the behavior of the balloons.

3. Predict which subatomic particle is most likely to be transferred during the rubbing. Give a reason for your choice.

Section 6.1

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Stable Atoms

• When the highest occupied energy level of an atom is filled with electrons, the atom is stable and not likely to react.

• We use electron dot diagrams to represent the number of valance electrons an atom has.

– Recall, each element in a family has the same number of valance electrons

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Electron Dot Diagrams for Some Group A Elements

Figure 2

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Ionic Bonding

• Stable atoms: Some elements become stable by transferring electrons between atoms

• As atoms gain and lose electrons they become positive or negatively charged. They form Ions

– Anion = negative charged ion

– Cation = positive charged ion

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Ionic Bonds

• Ionic bonds are bonds formed due to the attraction of oppositely charged ions.

– Sodium wants to lose an electron to become stable.

– Chlorine wants to gain an electron to become stable.

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Ionic compounds

• A chemical formula shows the elements in a compound, and what the ratio of elements is.

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Ionic Compounds

• In ionic bonds, each ion is attracted to all the neighboring ions with an opposite charge.

• This attraction keeps ions in a fixed position, creating a crystal lattice framework.

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More Ionic

Ionic Bonds are formed between metals and nonmetals.

Because they are formed between oppositely charged ions, they form a polar molecule.

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Interest Grabber

Ionic Compounds

Study the samples provided by your teacher. Use the list of properties of ionic compounds to determine which if any of the samples are ionic compounds.

Some properties of ionic compounds:

1. solid at room temperature

2. relatively high melting point

3. crystalline

4. brittle

Section 6.2

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Covalent Bonding

• Some atoms become stable by sharing electrons with other atoms

• A covalent bond is formed when two atoms share a pair of valance electrons.

Covalent bonds are formed between two nonmetals.

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Multiple covalent bonds

• Hydrogen shares only one pair of electrons, thus form single bonds

Other elements share multiple pairs of electrons, forming multiple bonds.

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Molecular Models of Hydrogen

Figure 9

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Unequal Sharing

• A covalent bond in which electrons are not shared equally is called a polar covalent bonds.

• The atom with the greater attraction for electrons has a partial negative charge

• The weaker atom has a partial positive charge

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Interest Grabber

Writing Formulas

The names of some compounds contain clues about their chemical formulas. Look at the names of the compounds below. Try to write a formula for each compound based on what you can derive from its name and what you know about the elements the compound contains. Explain how you determined each formula.

1. sulfur trioxide

2. magnesium bromide

3. iron (II) chloride

Section 6.3

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Binary molecules

• First write the name of the metal in the compound.

• Then write the root of the nonmetal in the compound.

– Finally, add the suffix –ide to the end of the nonmetal

– NaF this is sodium and fluorine

– The name of the compound is…

– Sodium Fluoride– Other common anions are on the next slide.

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Common Anions Figure 16

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Transition Metals

• When naming compounds with transition metals, always include the oxidation number for the transition metal

– CuCl this is copper and chlorine

– The name of this compound is …

– Copper (I) Chloride– Some common transition metals are on the next slide.

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Some Metal Cations Figure 17

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Some Polyatomic Ions Figure 19

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Writing formulae

• Write the symbol for the metal first

• Then write the symbol for the nonmetal

• Finally use the oxidation numbers to balance the compound.

– The oxidation numbers should add up to zero.

– Sodium Sulfide Na & S

– Na has a +1 oxidation number

– S has a -2 oxidation number.

– The formula is Na2S

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Polyatomic ions

• Writing the formulas for polyatomic compounds follow the same rules as other ionic compounds.

– The only acceptation is that if more than one polyatomic ion is needed, it needs to be put in (parenthesis).

– Calcium Nitrate The ate tells us that it’s a polyatomic ion

– Ca has a +2 charge

– NO3 has a -1 charge

– The formula is Ca(NO3)2

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Interest Grabber

Comparing Melting PointsThe table below compares the melting points of some metal elements, nonmetal elements, and ionic compounds. Study the table and answer the question.

Is bonding in metals more like bonding between nonmetals or bonding in ionic compounds? Give a reason for your answer.

Section 6.4

1330°CCalcite (CaCO3)Ionic Compounds 2825°CMagnesium Oxide

(MgO)

114°CIodine (I2)

115°CSulfur (S8)Nonmetals

1668°CTitanium (Ti)

1907°CChromium (Cr)Metals

Melting PointName

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Bonding and Malleability of a Metal

Figure 22

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• Identify the following as…

• Ionic or covalent?

• Polyatomic or binary?

• Metal or transition metal?

• Give the Name or Formula.

NaMnO4

PbCl4

PF3

Vanadium (III) Sulfide

Beryllium Oxide