IONIC, COVALENT, AND METALLIC COMPOUNDS

I. METALLIC COMPOUNDS

I. Metallic Compounds

• A metallic bond forms between a metal and a metal.
• Metals hold their electrons very loosely.
• Valence electrons are allowed to flow in a sea of electrons.
• Al & Al bonding:

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• This explains why metals are good conductors �(since moving e- creates electricity).

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II. IONIC COMPOUNDS

II. Ionic Compounds

• An ionic bond forms between a metal and a nonmetal. �(or a polyatomic ion).
• In an ionic bond, electrons are transferred from the metal to the nonmetal.
• Metals [lose or gain?] electrons to form �[positive or negative?] ions.
• Nonmetals [lose or gain?] electrons to form �[positive or negative?] ions.
• A positive ion and a negative ion will �[attract or repel?] each other. 🡨 This creates an � ionic bond!!!

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II. Ionic Compounds

• Example: Sodium & Chlorine

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• Animation

II. Ionic Compounds�-- Properties

• An Ionic Compound can also be called a salt.�Ex. NaCl, MgBr₂, Al₂O₃, CuCl₂ �video: http://www.youtube.com/watch?v=yjge1WdCFPs (0-39)
• When you dissolve an ionic compound in water, it can conduct electricity because the ions separate and are free to move around.��Moving charges = electricity!

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Show what happens during the formation of an Ionic Compound.

Step 1) Draw the Lewis dot diagrams.

Step 2) Show the transfer of electrons.

Step 3) Write down the resulting ions and the number of each ion as a subscript.

�Examples:

Lewis Dot Diagram Formula of Compound

• Na + Cl�

Show what happens during the formation of an Ionic Compound

Examples:

Lewis Dot Diagram Formula of Compound

• Mg + S�
• Ca + Cl�
• Li + S

Warm- Up

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Draw the Lewis dot diagram and formula of the compound by adding Mg+Br.

Writing the Formulas For Ionic Compounds: �Criss-Cross Method

Step 1) Write the charges.

Step 2) Positive ion always comes 1^st in the formula. � Negative ion comes 2^nd.

Step 3) Criss-Cross to find subscripts (no negative subscripts!!!). � - Subscripts tell you the number of each type of ion in the compound.

Step 4) Reduce to simplest ratio (just like a fraction). � - If the subscript is 1, you don’t have to write it.�

Writing the Formulas For Ionic Compounds: �Criss-Cross Method

• Examples:
• Na S �
• Al Br �
• Ca O �
• Cr⁴⁺ O

Polyatomic Ions

• Polyatomic ions are atoms that are bonded together with a covalent bond. When these atoms bond together, they act as a single unit and have a net charge.�Examples: OH^1-, PO₄^3-

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• A “poly”atomic ion is an ion that contains multiple atoms.

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• The polyatomic ion can bond with another ion to form a/an ionic compound.

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• See EOC Reference Tables.

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Polyatomic Ions

Writing the Formula for Ionic Compounds that Contain Polyatomic Ions

Step 1) Use the same criss-cross method that you used for binary ionic compounds (compounds with only 2 types of atoms).

Step 2) NEVER CHANGE THE SUBSCRIPT OF THE POLYATOMIC ION.�- Instead, add parentheses and put the subscript OUTSIDE the parentheses.

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Formulas with Polyatomic Ions - Examples

Al SO₄

Ca OH

Mg CO₃

Naming Ionic Compounds

Step 1) Write the name of the first element (or polyatomic ion).

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Step 2) Write the name of the second element & change the ending to –ide.

- Do not change the ending to –ide if it is a polyatomic ion.

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Naming Ionic Compounds

Examples:

• MgBr₂

• Li₂O

• Al₂(CO₃)₃

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Backwards! �Writing Formulas from Names

Examples:

• Barium chloride

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• Sodium sulfide

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• Aluminum chlorate

III. COVALENT (MOLECULAR) COMPOUNDS

Covalent (Molecular) Compounds

• A covalent bond between a nonmetal and a nonmetal.�
• Nonmetals hold their electrons very tightly. In a covalent bond, electrons are shared so that the octet rule is met.�video: http://www.youtube.com/watch?v=yjge1WdCFPs (40-end)
• Covalent compounds will not conduct electricity because they do not have ions.

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Show what happens during the formation of a covalent compound

Step 1) Draw the Lewis dot diagrams.�

Step 2) Draw a line to show the sharing of electrons.

• If 1 pair of e- is shared (__ total e-), it is a _______ bond.
• If 2 pairs of e- are shared (__ total e-), it is a ______ bond.
• If 3 pairs of e- are shared (__ total e-), it is a ______ bond.

Covalent Bonding�Examples

• Examples: ��A) H + Cl (HCl)

�B) Se + O (SeO)

�C) As + N (AsN)�

D) S + Br (SBr₂)

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Naming Covalent Compounds

• Use Prefixes!

1 – mono

2 – di

3 – tri

4 – tetra

5 – penta

6 – hexa

7 – hepta

8 – octa

9 – nona

10 – deca

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Naming Covalent (Molecular) Compounds

Step 1) Write the name of the first compound with a prefix to indicate the number of atoms.

- If there is only one atom of the first element, do not write “mono”.

Step 2) Write the name of the second compound with a prefix to indicate the number of atoms.

Step 3) Change the ending to –ide.

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** If there is an –ao or –oo when you add the prefix, drop the first vowel. �Ex: pentaoxide 🡪 pentoxide

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Naming Covalent Compounds

Examples:

A) P₂O₆�

B) NCl₅

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C) S₂Br₃

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D) SO₄

Prefixes (Memorize these!):

1 – mono

2 – di

3 – tri

4 – tetra

5 – penta

6 – hexa

7 – hepta

8 – octa

9 – nona

10 – deca

Backwards!�Write the formula from the name.

• The prefix tells you the number of each atom (the subscript)!

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• Example:
• Trinitrogen triphosphide
• Nitrogen tetroxide

How many atoms of each element?

Example:

• MgBr_2�
• Mg(NO₃)_2�
• Al(C₂H₃O₂)₃

Ionic or Covalent Compounds? Name these!

• MgBr₂

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• SO₃

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• Na₂SO₄

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• NH₄Br

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Write the formulas from the names – Mixed Practice

Examples:

• Aluminum oxide
• Dinitrogen pentoxide
• Sulfur trioxide
• Sodium sulfate

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