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Covalent Bonding (I) Sharing of Electrons in Single Bonds.

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Presentation on theme: "Covalent Bonding (I) Sharing of Electrons in Single Bonds."— Presentation transcript:

1 Covalent Bonding (I) Sharing of Electrons in Single Bonds

2 Covalent Bonds: Sharing of Electrons Non-metal with Non-metal Sharing of electron(s) –Non-polar (equal sharing of electrons) –Polar (uneven sharing of electrons) Weak bonds…low melting points –Single, double and triple bonds

3 Definitions Molecule: a neutral group of atoms united by covalent bonds. Nonpolar bond: a bond that has an equal sharing of bonding electrons. Polar bond: a bond that has an unequal sharing of bonding electrons. Unshared pair: a pair of electrons that is not involved in bonding but is instead held exclusively by one atom.

4 Nonmetal with Nonmetal Group 4A, 5A, 6A, 7A and Hydrogen Review of Lewis Dot Diagrams –Group 4A:C –Group 5A:N –Group 6AO –Group 7AF –HydrogenH

5 Covalent bonding FF l Fluorine has seven valence electrons l A second F atom also has seven l By sharing electrons …

6 Covalent bonding FF l By sharing electrons l Both end with full orbitals (stable octets) 8 Valence electrons

7 The Octet Rule Again with one Exception Most elements want to achieve 8 electrons after sharing in the their outer valence shell. Hydrogen wants to achieve 2 electrons after sharing in its outer valence shell. Shared electrons get counted for both partner atoms involved in the sharing of electrons.

8 Water H O Each hydrogen has 1 valence electron. Each hydrogen wants 1 more electron to get up to 2. Oxygen has 6 valence electrons. Oxygen wants 2 electrons to get up to 8. They share to make each other happy.

9 l Put the pieces together l The first hydrogen is happy l The oxygen still wants one more H O

10 Water l The second hydrogen attaches l Every atom has full energy levels l A pair of electrons is a single bond HO H H HO

11 11 Ammonia l NH 3 l N has 5 valence electrons, but wants 8 in a covalent compound. l H has 1 valence electrons, but wants 2 in a covalent compound. l 4 atoms with 3 bonds N H

12 N H H H Ammonia l Draw in the bonds l All 8 electrons are accounted for l Everything is full

13 Carbon dioxide l CO 2 - Carbon is the central atom (I have to tell you this) l Carbon has 4 valence electrons l Wants 4 more l Oxygen has 6 valence electrons l Wants 2 more OC

14 Carbon dioxide l Attaching 1 oxygen leaves the oxygen 1 short and the carbon 3 short O C

15 Carbon dioxide l Attaching the second oxygen leaves both oxygen 1 short and the carbon 2 short O C O

16 l The only solution is to share more l Requires two double bonds l Each atom gets to count all the atoms in the bond l 8 valence electrons Carbon dioxide O CO

17 l This shows all of the bonds. l Two double bonds, one between each oxygen and the central carbon. l Carbon dioxide O CO

18 More sharing examples O2O2 N2N2 O ONNOOO O NNNN NN double bond (2 pairs) triple bond (3 pairs) Share until octet is complete. octet complete

19 NaCl NaCl + - electron transfer and the formation of ions ionic bond This is the formation of an ionic bond. Cl Cl 2 covalent bond This is the formation of a covalent bond. sharing of a pair of electrons and the formation of molecules

20 ioniccovalent valence electrons Comparison of Bonding Types sharing of electrons transfer of electrons ions molecules  EN > 1.5  EN < 1.5 high mplow mp molten salts conductive non- conductive

21 Electronegativity (EN) - A measure of the ability of an atom in a compound to attract electrons

22 Electronegativity Difference: Ionic or Covalent Chlorides of Period 2 compound LiClBeCl 2 BCl 3 CCl 4 NCl 3 OCl 2 Cl 2  EN 0 Chlorides of Period 3 Compound NaClMgCl 2 AlCl 3 SiCl 4 PCl 3 SCl 6 Cl 2  EN large differencesmall difference The electronegativity difference:  EN = EN higher – EN lower

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