1. A look at ionic, covalent and metallic bonds
Chemical Bonds
A look at ionic, covalent and metallic bonds

2. Atom – the smallest unit of matter
Helium
atom

3. Electron Shells
Atomic number = number of Electrons
Electrons vary in the amount of energy they possess, and they occur at certain energy levels or electron shells.
Electron shells determine how an atom behaves when it encounters other atoms

4. Electrons are placed in shells according to rules:
The 1st shell can hold up to two electrons.
Each shell thereafter can hold up to 8 electrons.

5. H would like to
C would like to
N would like to
O would like to
Gain 1 electron
Gain 4 electrons
Gain 3 electrons
Gain 2 electrons

6. IONIC BOND A bond formed between two elements by the transfer of electrons

7. Formation of Ions from Metals
Ionic compounds result when metals react with nonmetals
Metals lose electrons to gain a full outer electron shell (the next electron shell becomes the new outer shell)
Positive ions form when electrons are lost
Group 1A metals  ion +1
Group 2A metals  ion +2
Group 3A metals  ion +3

8. Formation of Ions from Nonmetals
Nonmetals gain electrons to gain a full outer electron shell
Negative ions form when electrons are gained
Group 5A nonmetals  ion -3
Group 6A nonmetals  ion -2
Group 7A nonmetals  ion -1
Group 8A elements do not gain or lose electrons since they already have a full outer shell.

9. The formation of sodium chloride (salt)

10. Ionic Bonds: One Big Greedy Thief Dog!

11. 1). Ionic bond – electron from Na is transferred to Cl, this causes a charge imbalance in each atom. The Na becomes (Na+) and the Cl becomes (Cl-), charged particles or ions.

12. Properties of Ionic Compounds
Individual atoms are bound tightly together forming crystal structures
High melting points
High boiling points
Conduct electricity when melted or in solution
Many can be dissolved in water

14. COVALENT BOND A bond formed between two elements by the sharing of electrons.

15. How to Draw Covalent Bonds
1. Draw dot diagrams for each element
Figure out how many electrons need to be SHARED
Show sharing of electrons by connecting the dots.
Ex: Hydrogen and Oxygen.
H needs 2 valence e to be stable, O needs 8 total but only has 6.
They need to share electrons because they are both non-metals.

16. Example: Carbon + Chlorine

17. Covalent Bonds

18. when electrons are shared equally
NONPOLAR COVALENT BONDS
when electrons are shared equally
H2 or Cl2

19. Covalent bonds- Two atoms share one or more pairs of outer-shell electrons.
Oxygen Atom
Oxygen Atom
Oxygen Molecule (O2)

20. when electrons are shared but shared unequally
POLAR
COVALENT BONDS
when electrons are shared but shared unequally
H2O

21. Polar Covalent Bonds: Unevenly matched, but willing to share.

22. Water is a polar molecule because oxygen has a stronger charge than hydrogen, and therefore electrons are pulled closer to oxygen.

23. Properties of Covalent Compounds
Form irregular structures (no set geometric shapes like crystals)
Low melting and boiling points
Poor conductors of electricity in all phases
Many do not dissolve in water

24. METALLIC BOND Bond found in metals which holds metal atoms together very strongly

25. Metallic Bond
Formed between atoms of metallic elements
Electron cloud around atoms
Good conductors at all states, hard, very high melting points
Examples; Na, Fe, Al, Au, Co

26. Metallic Bond: A Sea of Electrons

27. Metallic Bonds: Mellow dogs with plenty of bones to go around.

28. Metals Form Alloys Metals do not combine with metals.
They form alloys which is a solution of a metal in a metal.
Three common examples are steel, brass, and bronze.

29. Examples of metal alloys