VII Atomic Structure C

1. VII Atomic Structure C Bonding

2. Bonding • Bonding between atoms in a compound comes from the sharing of electrons • The kind of bond formed between the two atoms depends on the amount of sharing of the electrons

3. Bonding in Compounds • Kinds of Bonds Ionic electron transferred from one atom to another generally between a metal cation and a non metal anion Covalent electrons shared between 2 atoms in a bond

4. Electronegativity • Measure of the ability of an atom in a bond to attract the bonding electrons • Across a Period: EN increases • Down a Group: EN decreases • Most electronegative element is fluorine Li Be B C N O F 1.0 1.5 2.0 2.5 3.0 3.5 4.0 Na Mg Al Si P S Cl 0.9 1.2 1.5 1.8 2.1 2.5 3.0 K Ca Ga Ge As Se Br 0.8 1.0 1.6 1.8 2.0 2.4 2.8

5. Determine the amount of covalent or ionic character in a bondUsing Electronegativity • The difference in electronegativity between two atoms can be used to determine how ionic or how covalent the bond is

6. Difference in electronegativity EN EN = 1.7 = 50% ionic EN > 1.7 more ionic EN < 1.7 more covalent The larger the EN, the more ionic the bond The smaller the EN, the more covalent the bond So the farther apart the atoms are the more ionic the bond

7. Compare three bonds: A) C--F B) O--F C) N--F Which is the most ionic?

8. Compare three bonds: A) C--F B) O--F C) N--F Which is the most covalent?

9. Determine the amount of covalent or ionic character in a bond • Fajan’s Rules of Covalency • The bond with the smaller cation is the more covalent bond • The bond with the larger anion is the more covalent bond • The bond with the larger charge on the cation or anion is the more covalent bond • The bond with a transition metal cation is the more covalent bond

10. Sb is smaller than Bi, so the SbCl3 is more covalent • Predict which is the more covalent • SbCl3 • BiCl3 • BeO • BeS • Tl2O • Tl2O3 • NaCl • CuCl S is larger than O, so the BeS is more covalent Compare Tl+ and Tl+3 , thallium(III) oxide more covalent Cu is a transition metal, CuCl more covalent

11. Which is the Most Covalent? • MgCl2 • MgBr2 • CaCl2 • CaBr2

12. Which is the Most Covalent? • MgCl2 • MgBr2 • CaCl2 • CaBr2 Compare: Mg cation and Ca cation. Mg smaller than Ca so Mg compounds more covalent Compare: Cl anion and Br anion. Br larger than Cl, so Br compounds more covalent

13. Which is the Most Ionic? • MgCl2 • MgBr2 • CaCl2 • CaBr2

14. Most ionic is the same as least covalent Which is the Most Ionic? • MgCl2 • MgBr2 • CaCl2 • CaBr2 Compare: Mg cation and Ca cation. Mg smaller than Ca so Mg compounds more covalent, Ca more ionic Compare: Cl anion and Br anion. Br larger than Cl, so Br compounds more covalent, Cl more ionic

15. Which of the following is least covalent? • Cu2O • CuO • Cu2S • CuS

16. Which of the following is least covalent? • Cu2O • CuO • Cu2S • CuS Compare anions O and S. S is the larger anion, so it forms more covalent bonds. Therefore, Cu2O and CuO are less covalent Cu2O is Cu+1, CuO is Cu+2 , the larger charge is more covalent, so Cu2O is the least covalent

17. Which of the following is least ionic? • AgCl • NaCl • AuCl • RbCl

18. Least ionic is Most covalent Which of the following is least ionic? • AgCl • NaCl • AuCl • RbCl Ag and Au are transition metals, so they are more covalent than Na and Rb which are Group 1 Alkali metals. Compare Ag and Au. Ag is the smaller size so it forms the most covalent bond.

19. Bond polarity • Because electrons are shared unequally in a bond due to the difference in electronegativity, a covalent bond has a positive end and a negative end. (poles) • The bond is said to be polar H ---Cl • Bond dipole - occurs when you have a polar bond • Dipole moment () - is a measure of the bond dipole (the amount of polarity) - +

20. Bond Polarity • The more ionic the bond the more polar the bond • The more ionic the bond, the larger the bond dipole • The more ionic the bond, the greater the dipole moment.

21. Compare three bonds: A) C--F B) O--F C) N--F Which is the least polar bond?