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 Li Be B C N O F 1.0 1.5 2.0 2.5 3.0 3.5 4.0
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
Na Mg Al Si P S Cl
K Ca Ga Ge As Se Br

5. Determine the amount of covalent or ionic character in a bond Using 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 = 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. Predict which is the more covalent SbCl3 BiCl3 BeO BeS Tl2O Tl2O3 NaCl
CuCl
Sb is smaller than Bi, so the SbCl3 is
more covalent
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. Which is the Most Ionic? MgCl2 MgBr2 CaCl2 CaBr2
Most ionic is the same as
least covalent
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. Which of the following is least ionic? AgCl NaCl AuCl RbCl
Least ionic is Most covalent
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?