1. Chemical Bonds
Section 2.3

2. Learning Objectives
Identify if a bond is covalent, ionic, or a hydrogen bond.
Explain how each type of bond forms & put them in order of increasing or decreasing strength.
Distinguish between polar and nonpolar molecules.

3. Atoms Are Held Together By Bonds
Chemical bonds are what hold atoms in a molecule together
Ex. Ionic, Covalent, and Hydrogen bonds
Bond energy = the energy needed to break a chemical bond
Electronegativity = a measure of how much an atom wants electrons

4. Covalent Bonds The SHARING of electrons
Each atom wants an octet in their valence shell

5. Chlorine
forms a
covalent
bond
with
itself
Cl2

6. How
will
two
chlorine
atoms
react? Cl Cl

7. Cl Cl Each chlorine atom wants to
gain one electron to achieve an octet

8. Cl Cl do to achieve an octet? What’s the solution – what can they
Neither atom will give up an electron –
chlorine is highly electronegative.
What’s the solution – what can they
do to achieve an octet?

9. Cl Cl

10. Cl Cl

11. Cl Cl

12. Cl Cl

13. Cl Cl
octet

14. Cl Cl
octet

15. Cl Cl The octet is achieved by each atom sharing the
electron pair in the middle

16. Cl Cl The octet is achieved by each atom sharing the
electron pair in the middle

17. Cl Cl
This is the bonding pair

18. Cl Cl
It is a single bonding pair

19. Cl Cl
It is called a SINGLE BOND

20. Single bonds are abbreviatedCl Cl
Single bonds are abbreviated
with a dash

21. This is the chlorine molecule,Cl Cl
This is the chlorine molecule,
Cl2

22. O2
Oxygen is also one of the diatomic molecules

23. O
How will two oxygen atoms bond?

24. O
Each atom has two unpaired electrons

25. O

26. O

27. O

28. O

29. O

30. O

31. O Oxygen atoms are highly electronegative.
So both atoms want to gain two electrons.

32. O Oxygen atoms are highly electronegative.
So both atoms want to gain two electrons.

33. O

34. O O

35. O O

36. O O

37. Both electron pairs are shared.

38. O O
6 valence electrons
plus 2 shared electrons
= full octet

39. O O
6 valence electrons
plus 2 shared electrons
= full octet

40. O O
two bonding pairs,
making a double bond

41. O O =
For convenience, the double bond
can be shown as two dashes.

42. This is the oxygen molecule,=
this is so cool!!
This is the oxygen molecule, O2

43. Two Types of Covalent Bonds
Polar = electrons are shared UNEQUALLY
One atom is more electronegative than the other atoms & pulls the electrons towards its atomic nucleus
A partial positive area & a partial negative area is created
Example – Water (H2O)

44. Nonpolar = electrons are shared EQUALLY
All atoms have similar electronegativities
The molecule has no charge

45. Ionic Bonds The TRANSFER of electrons
Electrons are moved from one atom to another atom to achieve a full valence shell

46. Ionic Bonding Creates Ions
Ion = an atom with a positive or negative charge due to having unequal numbers of protons & electrons
Cation = ion with a positive (+) charge
Anion = ion with a negative (-) charge

47. Ions are attracted to each other because of their opposite charges
Just like a magnet
Ionic compounds easily dissociate (separate) in water

48. Hydrogen Bonds
Partial positive charge of a hydrogen is attracted to the partial negative charge of another polar molecule
Weak by themselves
Strong together
Easily formed & broken

49. Solutions Solvent = does the dissolving Solute = is dissolved
The liquid part
Water is an excellent solvent because the polar ends surround ions of the opposite charge
Prevents ions from bonding back together
Solute = is dissolved
The solid