1. Chemical Bonding

2. Electron Cloud
Electrons are located around the nucleus in the electron cloud.
The cloud is arranged into levels called shells or energy levels.
The elements in a period have the same number of levels or shells.
1st Period = 1 Shell
2nd Period = 2 Shells
3rd Period = 3 Shells
4th Period = 4 Shells

3. Electrons Remember from Chapter 4- each column is called a group.
Each element in a group has the same number of electrons in their outer orbital, or “shell”.
Each shell can hold a specific number of electrons
1st= 2 electrons
2nd= 8 electrons
3rd= 8 electrons
A shell must be filled before moving to the next level
The electrons in the outer shell are called “valence electrons”

4. Turn to your periodic table and label…
Group 8 = 8 electrons
Group 1 = 1 electron
Except for He, it has 2 electrons
Group 2 = 2 electrons 3 4 5 7 6

5. Determine the number of shells and the number of valence electrons to create Bohr Diagram for:
Carbon - C
2nd Period = 2 shells
4th Group =
4 valence
electrons

6. Now you try: Ne Name the element. Number of shells ?
Valence electrons ?
Neon
2nd Period = 2 shells
8th Group = 8 valence electrons

7. Be Try another: Name the element. Number of shells ?
Valence electrons ?
Beryllium
2nd Period = 2 shells
2nd Group = 2 valence electrons

8. S Last one: Name the element. Number of shells ? Valence electrons ?
Sulfur
3rd Period = 3 shells
6th Group = 6 valence electrons

9. Electron Dot Diagrams & Chemical Bonding

10. The goal of an atom The goal of an atom is to be “happy.”
An atom is happy when it has a full outer energy level

11. How many valence electrons does this need to be “happy?”
A. B.

12. How many valence electrons does this need to be “happy?”
C. D.

13. How many valence electrons does this need to be “happy?”
E F.

14. How to draw Electron Dot Diagram
Step 1: Write down Element symbol
Step 2: Find out how many valence electrons there are
Step 3: Place electrons around the symbol one at a time and if there is enough double up
O= 6 ValenceElectrons

15. Some common Examples Sodium Na 1 valence electron 2. Argon Ar
8 valence electrons

16. Practice Problems
Use your periodic table to find the number of valence electrons for each of the following. Then, draw an Electron Dot Diagram for each.
Carbon
Lithium
Krypton
Boron
Neon
Nitrogen
Flourine
Helium
Aluminum
Calcium

17. Chemical Bonding
Chemical Bonding- combining of atoms to form molecules or ionic compounds
Chemical Bond- what holds the atoms together

18. Periodic Table
Remember from last week, the periodic table tells you how many valence electrons an atom has.
If we know the number of valence electrons, we can figure out which atoms combine and how.

19. Noble Gases All have 8 valence electrons except Helium which has 2
All of these atoms are happy because their outer shell is full.
Since they are happy, they are not likely to form compounds.

20. Three types of Bonding Ionic- between metal/nonmetal
Covalent- between nonmetals
Metallic- between metals

21. Ionic Bonding
Ionic Bonding- bond that forms when electrons are transferred from one atom to another
Ions- charged particles that form when an atom gains or loses electrons
This occurs between a metal and a nonmetal
Polyatomic ion- ionic bond with more than one bond
NaOH and NO3

22. These are both the same element. How?
A B.
What is the element for A?
How many valence electrons are missing from A to make it happy?
Is it easier to gain 5 electrons or lose 3 electrons?
What is the name for B?

23. Gain or Lose If you lose electrons, the charge becomes a positive
If you gain electrons, the charge becomes a negative

24. What bonds with what? Positive charges bond with negative charges
Positive always is written first
You may have to increase the number of atoms to balance the bond

25. Cheat

26. Ionic Bonding Steps
Using 2 different colors, draw the electron dot diagram for each atom
Decide whether each will gain or lose electrons
Draw arrows to show where the electrons are transferred
Write in the new charge for each molecule

27. Ionic Bonding Bond Sodium(Na) with Fluorine(F).
Bond Beryllium(Be) with Oxygen(O).
Bond Aluminum(Al) with Phosphorus(P).
Bond Magnesium(Mg) with Sulfur(S).

28. Cross Bonding Good when charges are not equal
Bond Aluminum with sulfur
Top number loses charge and goes to bottom number
Al+3 S-2
Al2 S3
Answer=Al2S3

29. Now try cross bonding yourself
Bond Fluorine with Boron
Bond Aluminum with Selenium
Bond Chlorine with Gallium
Bond Silicon with Sulfur.

30. Covalent Bonds
Covalent bond- formed when atoms share one or more pairs of electrons these form molecules
Shared Electrons H H

31. 2 different types of covalent bonds
Polar bonds- electrons are shared unequally
Nonpolar bonds- electrons are shared equally

32. Covalent Bond
H2O

33. Steps for Covalent Bonding
Draw the EDD for all elements
Look for ways to make the “puzzle pieces” fit together
If two elements are sharing an electron it will be on the same side

34. Water is made of covalent bonds

35. Charge vs. Number
B+3O-2
B2O3
charge
TOP
how many
BOTTOM

36. Now try drawing some on your own!
NH3
H2S
CH4
Cl2
CO2

37. Metallic Bond
Metallic bond- attraction between a positive metal ion and the electrons surrounding it
Alloy- has two or more metals that are bonding together

38. Alloy Properties Resist rust Ductile-put into a wire
Malleable- flattened into sheets

39. Properties of Covalent bonds
Low melting points
Poor conductivity
Do not break up into ions

40. Properties of Ionic Forms ionic crystals Has high melting points
Bonds are broken by electricity

41. Make the following molecules using puzzle pieces:
CO2
C2H4 F2
C2H6
Cl2
H2O O2
C2H2 N2
Br2 I2
NH3
PCl3
CH4
SiO2