Chemical bonding

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Chemical bonding

  1. 1. Chemical Bonding
  2. 2. CHEMICAL BONDS <ul><li>A chemical bond is the force that holds atoms together. </li></ul><ul><li>There are 3 types of bonds: </li></ul><ul><li>Ionic bond </li></ul><ul><li>Covalent bond </li></ul><ul><li>Metallic bond </li></ul>
  3. 3. Chemical bond <ul><li>Chemical bonds can form : </li></ul><ul><li>A) By the attraction between opposite charged ions </li></ul><ul><li>B) By the sharing of electrons between atoms </li></ul>
  4. 4. Positive Ion Formation <ul><li>A positive ion forms when an atom loses one or more valence electrons in order to attain a noble gas configuration (octet rule). </li></ul><ul><li>A positively charged ion is called a cation </li></ul><ul><li>Ex. </li></ul>
  5. 5. Metal Ions <ul><li>Metals atoms are reactive because they lose valence electrons easily, have Low ionization energy and low electron affinity </li></ul><ul><li>The group 1 and 2 metals are the most reactive metals in the P.T. </li></ul><ul><li>Metals in group 1 form +1 ions </li></ul><ul><li>Metals in group 2 form +2 ions </li></ul><ul><li>Metals in group 13 form +3 ions </li></ul><ul><li>Transition metals: is difficult to predict </li></ul>
  6. 6. Negative Ion Formation <ul><li>Nonmetals, located on the right side of the P.T., easily gain electrons to attain a stable outer configuration(octet rule) and form an anion. </li></ul>
  7. 7. Nonmetal Ions <ul><li>Elements in group 15 gain 3 electrons and form -3 ions </li></ul><ul><li>Elements in group 16 gain 2 electrons and form -2 ions </li></ul><ul><li>Elements in group 17 gain 1 electron and form -1 ions </li></ul>
  8. 8. Lewis dot diagrams for Ions
  9. 9. Practice <ul><li>Write the symbol of the ion and the dot structure of the following : </li></ul><ul><li>a)calcium ion </li></ul><ul><li>b) germanium ion </li></ul><ul><li>c) phosphide </li></ul><ul><li>d) oxide </li></ul>
  10. 10. The Ionic Bond
  11. 11. Na e.c. 2,8,1 (Na + ) Ion Atom e.c. (2,8) + The Sodium loses 1 electron to leave a complete outer shell. It is now a Sodium ion with a charge of 1 + The Sodium atom has 1 Electron in it’s outer shell. +
  12. 12. Cl e.c. 2,8,7 (Cl - ) Ion Atom e.c. (2,8,8) - The Chlorine gains 1 electron to gain a complete outer shell. It is now a Chlorine ion with a charge of 1 - The Chlorine atom has 7 electrons in it’s outer shell. -
  13. 13. Sodium atom Na Sodium ion (Na + ) Chlorine atom Cl Chlorine ion (Cl - ) The Ionic Bond The sodium atom loses one electron to attain a complete outer shell and become a positive ion (Na + ). The Chlorine atom gains one electron to attain a complete outer shell and become a negative ion (Cl – ). Strong electrostatic forces attract the sodium and chlorine ions. + -
  14. 14. Ionic Bonds
  15. 16. Ion Cartoon
  16. 17. Covalent Bonds <ul><li>Atoms in nonionic compounds share electrons. </li></ul><ul><li>A molecule is formed when 2 or more atoms bond covalently. </li></ul><ul><li>The majority of covalent bonds form between atoms of nonmetallic elements. </li></ul>
  17. 18. Covalent Bonds
  18. 19. Covalent Bonds
  19. 20. Covalent bonds can be single, double or triple <ul><li>Single covalent bond: atoms share 1 pair of electrons </li></ul><ul><li>Double covalent bond: atoms share 2 pairs of electrons </li></ul><ul><li>Triple covalent bond: atoms share 3 pairs of electrons </li></ul>
  20. 21. Covalent bonds
  21. 22. Covalent bonds <ul><li>The halogens, group 17, form single covalent bonds with atoms of other nonmetals. They can only form 1 bond since they have 7 valence electrons. </li></ul><ul><li>The chalcogens, group 16, have 6 valence electrons, can form a total of 2 bonds . These can be single or double. </li></ul><ul><li>The group 15 elements, have 5 valence electrons, can form a total of 3 bonds . These can be single, double or triple. </li></ul>
  22. 23. Practice <ul><li>Draw the Lewis structures for each molecule: </li></ul><ul><li>a) PH3 </li></ul><ul><li>b) H2S </li></ul><ul><li>c) HCl </li></ul><ul><li>d) CCl4 </li></ul><ul><li>e) SiH4 </li></ul><ul><li>f) OBr2 </li></ul>
  23. 24. Electronegativity and Polarity <ul><li>The type of bond formed is related to each atom´s attraction for electrons. </li></ul><ul><li>Electronegativity indicates the relative ability of an element´s atoms to attract electrons in a chemical bond. </li></ul><ul><li>Nonmetals have higher electronegativities than do metals. </li></ul><ul><li>Each element is assigned a value: </li></ul>
  24. 25. Electronegativity
  25. 26. Types of Bonds
  26. 27. Types of bonds <ul><li>Bond can be: polar covalent, nonpolar covalent and ionic. </li></ul><ul><li>Polar bond: a bond in which electrons are shared unequally. </li></ul><ul><li>Nonpolar bond: a bond in which electrons are shared equally. </li></ul><ul><li>Ionic bond: a bond in which electrons are transferred. </li></ul><ul><li>The character of a bond depends on how strongly each of the bonded atoms attracts electrons. </li></ul>
  27. 28. Practice <ul><li>Use electronegativities to classify each of the following bonds as nonpolar covalent, polar covalent or ionic: </li></ul><ul><li>a) O-H </li></ul><ul><li>b) O-K </li></ul><ul><li>c) Cl- As </li></ul><ul><li>d) N -N </li></ul>
  28. 29. POLARITY OF MOLECULES <ul><li>Nonpolar molecules: are molecules that have a symmetrical arrangement and the dipoles cancel each other. </li></ul><ul><li>Polar molecules: one end of the molecule is more negatively charged than the other end, have a dipole. </li></ul>
  29. 30. POLARITY OF MOLECULES
  30. 31. PRACTICE <ul><li>Indicate if each of the following molecules is polar or nonpolar: </li></ul><ul><li>a) BF3 </li></ul><ul><li>b) CH3F </li></ul><ul><li>c) CCl4 </li></ul><ul><li>d) NF3 </li></ul><ul><li>e) Br2 </li></ul>
  31. 32. IONIC AND COVALENT COMPOUNDS IONIC COVALENT METALLIC TYPE OF PARTICLE PHYSICAL STATE MELTING POINT ELECTRIC CONDUCTIVITY SOLUBILITY EXAMPLES

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