1. Chemical Bonding

2. CHEMICAL BONDS A chemical bond is the force that holds atoms together.
There are 3 types of bonds:
Ionic bond
Covalent bond
Metallic bond

3. Chemical bond Chemical bonds can form :
A) By the attraction between opposite charged ions
B) By the sharing of electrons between atoms

4. Positive Ion Formation
A positive ion forms when an atom loses one or more valence electrons in order to attain a noble gas configuration (octet rule).
A positively charged ion is called a cation
Ex.

5. Metal Ions
Metals atoms are reactive because they lose valence electrons easily, have Low ionization energy and low electron affinity
The group 1 and 2 metals are the most reactive metals in the P.T.
Metals in group 1 form +1 ions
Metals in group 2 form +2 ions
Metals in group 13 form +3 ions
Transition metals: is difficult to predict

6. Negative Ion Formation
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.

7. Nonmetal Ions Elements in group 15 gain 3 electrons and form -3 ions
Elements in group 17 gain 1 electron and form -1 ions

8. Lewis dot diagrams for Ions

9. Practice
Write the symbol of the ion and the dot structure of the following :
a)calcium ion
b) germanium ion
c) phosphide
d) oxide

10. The Ionic Bond

11. + The Sodium atom has 1 Electron in it’s outer shell.Na
e.c. 2,8,1
Atom +
The Sodium loses 1 electron to leave a complete outer shell.
It is now a Sodium ion with a charge of 1 +
(Na +)
e.c. (2,8)+
Ion

12. - The Chlorine atom has 7 electrons in it’s outer shell.Cl
e.c. 2,8,7
Atom -
(Cl - )
The Chlorine gains 1 electron to gain a complete outer shell.
It is now a Chlorine ion with a charge of 1 -
e.c. (2,8,8)-
Ion

13. + - The Ionic Bond Sodium atom Na Chlorine atom Cl Sodium ion (Na +)
Chlorine ion
(Cl -)
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. Ionic Bonds

16. Ion Cartoon

17. Covalent Bonds Atoms in nonionic compounds share electrons.
A molecule is formed when 2 or more atoms bond covalently.
The majority of covalent bonds form between atoms of nonmetallic elements.

18. Covalent Bonds

19. Covalent Bonds

20. Covalent bonds can be single, double or triple
Single covalent bond: atoms share 1 pair of electrons
Double covalent bond: atoms share 2 pairs of electrons
Triple covalent bond: atoms share 3 pairs of electrons

21. Covalent bonds

22. Covalent bonds
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.
The chalcogens, group 16, have 6 valence electrons, can form a total of 2 bonds. These can be single or double.
The group 15 elements, have 5 valence electrons, can form a total of 3 bonds. These can be single, double or triple.

23. Practice Draw the Lewis structures for each molecule: a) PH3 b) H2S
c) HCl
d) CCl4
e) SiH4
f) OBr2

24. Electronegativity and Polarity
The type of bond formed is related to each atom´s attraction for electrons.
Electronegativity indicates the relative ability of an element´s atoms to attract electrons in a chemical bond.
Nonmetals have higher electronegativities than do metals.
Each element is assigned a value:

25. Electronegativity

26. Types of Bonds

27. Types of bonds
Bond can be: polar covalent, nonpolar covalent and ionic.
Polar bond: a bond in which electrons are shared unequally.
Nonpolar bond: a bond in which electrons are shared equally.
Ionic bond: a bond in which electrons are transferred.
The character of a bond depends on how strongly each of the bonded atoms attracts electrons.

28. Practice
Use electronegativities to classify each of the following bonds as nonpolar covalent, polar covalent or ionic:
a) O-H
b) O-K
c) Cl- As
d) N -N

29. POLARITY OF MOLECULES
Nonpolar molecules: are molecules that have a symmetrical arrangement and the dipoles cancel each other.
Polar molecules: one end of the molecule is more negatively charged than the other end, have a dipole.

30. POLARITY OF MOLECULES

31. PRACTICE
Indicate if each of the following molecules is polar or nonpolar:
a) BF3
b) CH3F
c) CCl4
d) NF3
e) Br2

32. IONIC AND COVALENT COMPOUNDS
METALLIC
TYPE OF PARTICLE
PHYSICAL STATE
MELTING POINT
ELECTRIC CONDUCTIVITY
SOLUBILITY
EXAMPLES