2.
Review.. <ul><li>What is a chemical bond? </li></ul><ul><ul><li>Force that holds two atoms together </li></ul></ul><ul><li>What is an ionic bond? </li></ul><ul><ul><li>An electrostatic force that holds oppositely charged particles together in an ionic compound </li></ul></ul><ul><ul><li>Forms when….? </li></ul></ul><ul><li>What are atoms and compounds always trying to achieve? </li></ul><ul><ul><li>Stability </li></ul></ul><ul><ul><li>Complete set of valence electrons… </li></ul></ul>
3.
What is a covalent bond? <ul><li>Chemical bond that results from sharing of valence electrons </li></ul>
4.
Which bond is stronger? <ul><li>Ionic vs. Covalent </li></ul><ul><li>Remember…. </li></ul><ul><ul><li>Ionic compounds are in a crystal lattice…many ions are bonded together in a crystal lattice </li></ul></ul><ul><ul><li>Covalent compounds are neutral and often found in the form of individual molecules </li></ul></ul><ul><ul><li>Ionic bonds are stronger than covalent bonds </li></ul></ul>
5.
How are covalent bonds formed? <ul><li>Charge of nucleus? </li></ul><ul><li>Charge of electron cloud? </li></ul><ul><li>What happens when 2 fluorine atoms approach each other? </li></ul><ul><li>Covalent bond occurs at “Point of maximum attraction” </li></ul><ul><ul><li>Attractive forces of nucleus for electrons and repulsive forces of electrons in each atom balance out </li></ul></ul><ul><ul><li>What would happen if the atoms kept moving closer? </li></ul></ul>
6.
What is a Molecule? <ul><li>Compound made when two or more atoms bond together covalently </li></ul><ul><li>Diatomic molecules </li></ul><ul><ul><li>In nature, sometimes two atoms of the same element are more stable when they are covalently bonded than the individual atom alone… </li></ul></ul><ul><ul><li>BrINClHOF </li></ul></ul><ul><ul><li>Br 2 I 2 N 2 Cl 2 H 2 O 2 F 2 </li></ul></ul>
7.
Types of electrons in molecule <ul><li>Look at fluorine </li></ul><ul><li>What is the electron configuration? </li></ul><ul><ul><li>1s 2 2s 2 2p 5 </li></ul></ul><ul><li>How many Valance electrons? </li></ul><ul><ul><li>7 </li></ul></ul><ul><li>Dot Structure? </li></ul><ul><li>What would two F atoms look like covalently bonded? </li></ul>
8.
<ul><li>BONDING PAIRS are electrons involved in the covalent bond (shared electrons) </li></ul><ul><li>The pairs of electrons that are NOT involved in the covalent bond are called the LONE PAIRS (unshared electrons) </li></ul><ul><li>What are the lone pairs in… </li></ul>
9.
In the fluorine molecule… <ul><li>How many bonding pairs are there in each? </li></ul><ul><ul><li>1 </li></ul></ul><ul><li>How many lone pairs are there each? </li></ul><ul><ul><li>3 </li></ul></ul>
10.
Lewis Dot Diagrams <ul><li>When writing out molecules… </li></ul><ul><ul><li>Bonding pairs can be represented by the electrons themselves or by a single line </li></ul></ul><ul><ul><li>If there is more than one bonding pair, two lines are used </li></ul></ul><ul><ul><li>Up to four lines can be used </li></ul></ul><ul><ul><li>EACH LINE REPRESENTS A BONDING PAIR OF ELECTRONS IN A MOLECULE </li></ul></ul><ul><ul><li>1 line=2 electrons </li></ul></ul><ul><ul><li>Lines represent bonding pairs…you must still draw out lone pairs </li></ul></ul>
11.
3 basic rules <ul><li>Sum up valence electrons of all atoms in the molecule </li></ul><ul><li>Use a pair of electrons to form a bond between atoms…use a line to represent bond </li></ul><ul><li>Arrange remaining electrons to satisfy the duet rule for hydrogen and the octet rule for other atoms </li></ul><ul><li>(Verify that each atom has a complete set of electrons ) </li></ul>
12.
<ul><li>Elements is group 7A have how many valence electrons? </li></ul><ul><ul><li>How many electrons would they share in a covalent bond with an atom in group 7A? </li></ul></ul><ul><ul><li>How many covalent bonds do are formed between bonding atoms in 7A? </li></ul></ul><ul><li>Elements in group 6A have how many valence electrons? </li></ul><ul><ul><li>How many electrons would they have to share in a covalent bond with another atom in group 6A? </li></ul></ul><ul><ul><li>How many covalent bonds do are formed between bonding atoms in 6A? </li></ul></ul>
13.
<ul><li>Elements in group 5A have how many valence electrons? </li></ul><ul><ul><li>How many electrons would they have to share in a covalent bond with another atom in group 5A? </li></ul></ul><ul><ul><li>How many covalent bonds do are formed between bonding atoms in 5A? </li></ul></ul><ul><li>Elements in group 4A have how many valence electrons? </li></ul><ul><ul><li>How many electrons would they have to share in a covalent bond to be stable? </li></ul></ul><ul><ul><li>How many covalent bonds are formed between bonding atoms in group 4A? </li></ul></ul>
14.
Writing Chemical Equations showing covalent bond formation <ul><li>See board… </li></ul>
15.
Classwork…to turn in… <ul><li>1. PH 3 </li></ul><ul><li>2. H 2 S </li></ul><ul><li>3. HCl </li></ul><ul><li>4. CCl 4 </li></ul><ul><li>5. SiH 4 </li></ul>6. HF 7. N 2 8. CH 4 9. CF 4 <ul><li>Show the formation of the following molecules…your final answer should be the correct Lewis Dot Structure </li></ul>
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